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2012 Volume 28 Issue 1
2012, 28(01):
Abstract:
2012, 28(01): 1-18
doi: 10.3866/PKU.WHXB2012281
Abstract:
Atomic charge is one of the simplest and the most intuitive description of charge distribution in chemical systems. It has great significance in theory and in practical applications. In this article we introduce the basic principles and special characteristics of twelve important computational methods for the determination of atomic charges and compare their pros and cons from various aspects by considering a large number of instances. These methods include Mulliken, atomic orbitals in molecules (AOIM), Hirshfeld, atomic dipole moment corrected Hirshfeld population (ADCH), natural population analysis (NPA), Merz-Kollmann (MK), atom in molecules (AIM), Merck molecular force field 94 (MMFF94), AM1-BCC, Gasteiger, charge model 2 (CM2), and charge equilibration (QEq). Finally some general suggestions on how to choose a proper method for practical applications are given.
Atomic charge is one of the simplest and the most intuitive description of charge distribution in chemical systems. It has great significance in theory and in practical applications. In this article we introduce the basic principles and special characteristics of twelve important computational methods for the determination of atomic charges and compare their pros and cons from various aspects by considering a large number of instances. These methods include Mulliken, atomic orbitals in molecules (AOIM), Hirshfeld, atomic dipole moment corrected Hirshfeld population (ADCH), natural population analysis (NPA), Merz-Kollmann (MK), atom in molecules (AIM), Merck molecular force field 94 (MMFF94), AM1-BCC, Gasteiger, charge model 2 (CM2), and charge equilibration (QEq). Finally some general suggestions on how to choose a proper method for practical applications are given.
2012, 28(01): 19-24
doi: 10.3866/PKU.WHXB20122819
Abstract:
The bond valence parameters (R0) for homoleptic Sn(II)―X and Sn(IV)―X complexes, where X=O, S, N, C, P, As, Se, Te, F, Cl, Br, and I, were determined using data retrieved from the Cambridge Structural Database with bond valence parameter B=0.037 nm. Some are the first reported experimental values for Sn(II)―X or Sn(IV)―X bonds. In the case of Sn(II)―O, R0=0.1956 nm with B=0.037 nm can be used to assign the oxidation state of the central Sn(II) ion for almost all coordination numbers. In contrast, the reported parameter set of R0=0.1859 nm with B=0.055 nm appears applicable mainly to complexes with a low coordination number. Our results suggest that further studies of bond valence parameters are required to better understand the factors that are important in bond valence sum (BVS) calculations.
The bond valence parameters (R0) for homoleptic Sn(II)―X and Sn(IV)―X complexes, where X=O, S, N, C, P, As, Se, Te, F, Cl, Br, and I, were determined using data retrieved from the Cambridge Structural Database with bond valence parameter B=0.037 nm. Some are the first reported experimental values for Sn(II)―X or Sn(IV)―X bonds. In the case of Sn(II)―O, R0=0.1956 nm with B=0.037 nm can be used to assign the oxidation state of the central Sn(II) ion for almost all coordination numbers. In contrast, the reported parameter set of R0=0.1859 nm with B=0.055 nm appears applicable mainly to complexes with a low coordination number. Our results suggest that further studies of bond valence parameters are required to better understand the factors that are important in bond valence sum (BVS) calculations.
2012, 28(01): 25-36
doi: 10.3866/PKU.WHXB20122825
Abstract:
The thermal behavior of humic acids of fusain (F-HA) and humic acids of demineralized fusain (DF-HA) were investigated at heating rates of 5, 20, and 50 °C·min-1 using an open system thermogravimetric analyzer coupled to a quadrupole thermogravimetry mass spectrometer (TG-MS). The pyrolytic and hydrogen generation kinetics were analyzed using the distributed activation energy model (DAEM) and the distribution functions of the activation energy were obtained. The results indicated: (1) the distribution function of the activation energy for F-HA has an asymptotic approximation to a Gaussian distribution during pyrolysis. Moreover, it has some symmetry properties and the same peak value as a standard Gaussian distribution. The distribution function of the activation energy for DF-HA has an asymptotic approximation to a Gaussian distribution during pyrolysis and its peak value is less than that of a standard Gaussian distribution. According to the conversion ratio vs temperature, activation energy relationships and the thermal mass loss features of humic acids, four and five stages of a general pyrolytic process were found for F-HA and DF-HA, respectively. The chemical reactions for each stage of the pyrolytic process are discussed in detail. (2) The distribution functions of the activation energy of hydrogen generation for F-HA and DF-HA have an asymptotic approximation to a Gaussian distribution during pyrolysis. The activation energy of hydrogen generation increased with an increase in the conversion yields but it also showed staged features. Based on the kinetic characteristics of their generation during pyrolysis their hydrogen generation processes can be divided into five stages, which reflect the different chemical reaction mechanisms. (3) The demineralization of Yimin fusain influences the thermal behavior, kinetics of the pyrolytic processes and the hydrogen generation of humic acid.
The thermal behavior of humic acids of fusain (F-HA) and humic acids of demineralized fusain (DF-HA) were investigated at heating rates of 5, 20, and 50 °C·min-1 using an open system thermogravimetric analyzer coupled to a quadrupole thermogravimetry mass spectrometer (TG-MS). The pyrolytic and hydrogen generation kinetics were analyzed using the distributed activation energy model (DAEM) and the distribution functions of the activation energy were obtained. The results indicated: (1) the distribution function of the activation energy for F-HA has an asymptotic approximation to a Gaussian distribution during pyrolysis. Moreover, it has some symmetry properties and the same peak value as a standard Gaussian distribution. The distribution function of the activation energy for DF-HA has an asymptotic approximation to a Gaussian distribution during pyrolysis and its peak value is less than that of a standard Gaussian distribution. According to the conversion ratio vs temperature, activation energy relationships and the thermal mass loss features of humic acids, four and five stages of a general pyrolytic process were found for F-HA and DF-HA, respectively. The chemical reactions for each stage of the pyrolytic process are discussed in detail. (2) The distribution functions of the activation energy of hydrogen generation for F-HA and DF-HA have an asymptotic approximation to a Gaussian distribution during pyrolysis. The activation energy of hydrogen generation increased with an increase in the conversion yields but it also showed staged features. Based on the kinetic characteristics of their generation during pyrolysis their hydrogen generation processes can be divided into five stages, which reflect the different chemical reaction mechanisms. (3) The demineralization of Yimin fusain influences the thermal behavior, kinetics of the pyrolytic processes and the hydrogen generation of humic acid.
2012, 28(01): 37-43
doi: 10.3866/PKU.WHXB201111172
Abstract:
The Fe-P binary system was reoptimized by means of the CALPHAD approach. The Gibbs energy descriptions of every phase in the Fe-P binary system were optimized based on the latest experimental thermodynamic and phase diagram data. The solution phase (liquid, α-Fe, and γ-Fe) was described by the substitutional solution approximation and the other phases (Fe3P, Fe2P, FeP, FeP2, and FeP4) were treated as the stoichiometric compounds. The optimization was carried out using the Thermo-Calc® software package. The agreement of the optimized phase diagram and thermodynamic data with experimental results is od, and a self-consistent and reliable thermodynamic dataset is obtained to allow further optimization of Fe-based, P-containing multicomponent alloy systems.
The Fe-P binary system was reoptimized by means of the CALPHAD approach. The Gibbs energy descriptions of every phase in the Fe-P binary system were optimized based on the latest experimental thermodynamic and phase diagram data. The solution phase (liquid, α-Fe, and γ-Fe) was described by the substitutional solution approximation and the other phases (Fe3P, Fe2P, FeP, FeP2, and FeP4) were treated as the stoichiometric compounds. The optimization was carried out using the Thermo-Calc® software package. The agreement of the optimized phase diagram and thermodynamic data with experimental results is od, and a self-consistent and reliable thermodynamic dataset is obtained to allow further optimization of Fe-based, P-containing multicomponent alloy systems.
2012, 28(01): 44-50
doi: 10.3866/PKU.WHXB20122844
Abstract:
Density functional theory (DFT) calculations were used to investigate the structural and electronic properties of V-, Cr-, Pd-, Pt-, and Au-doped titania nanotube arrays (TNTAs) where Ti was replaced by dopants. The adsorption of CO and the formation of CO2 on these various nanotube arrays were also studied in detail. We found that CO physisorbed weakly inside the TNTAs and CO was oxidized by lattice oxygen to form CO2 by the redox mechanism. This may thus be attributed to the unique confinement effect and to different metal doping. All the metal doped systems except the Cr-TNTAs showed a lower activation energy barrier than the undoped TNTAs, indicating that proper metal dopants can promote CO oxidation. The reaction on the Pd- or Au-doped TNTAs had the lowest barrier. Therefore, we found that Pd- or Au-doped TNTAs led to enhanced catalytic activity for CO oxidation at low temperatures.
Density functional theory (DFT) calculations were used to investigate the structural and electronic properties of V-, Cr-, Pd-, Pt-, and Au-doped titania nanotube arrays (TNTAs) where Ti was replaced by dopants. The adsorption of CO and the formation of CO2 on these various nanotube arrays were also studied in detail. We found that CO physisorbed weakly inside the TNTAs and CO was oxidized by lattice oxygen to form CO2 by the redox mechanism. This may thus be attributed to the unique confinement effect and to different metal doping. All the metal doped systems except the Cr-TNTAs showed a lower activation energy barrier than the undoped TNTAs, indicating that proper metal dopants can promote CO oxidation. The reaction on the Pd- or Au-doped TNTAs had the lowest barrier. Therefore, we found that Pd- or Au-doped TNTAs led to enhanced catalytic activity for CO oxidation at low temperatures.
2012, 28(01): 51-57
doi: 10.3866/PKU.WHXB20122851
Abstract:
We studied the adsorption of CO molecules on perfect and Pt-adsorbed t-ZrO2(101) surfaces using a periodic slab model by PW91 of generalized gradient approximation (GGA) within the framework of density functional theory. The results indicated that the second sub-surface oxygen and the second bridge sites are the most stable adsorbed sites for CO and Pt on the ZrO2(101) surface, respectively. When the coverage is 0.25 ML (monolayer) the most stable models were obtained with adsorption energies of 56.2 and 352.7 kJ·mol-1. The most stable model of CO adsorbed on the Pt/t-ZrO2(101) surface was obtained by C-end adsorption with an adsorption energy of 323.8 kJ·mol-1. We considered vibrational frequency calculations, density of states and the Mulliken population of the adsorption systems before and after adsorption and these were compared for CO and Pt adsorption onto the ZrO2 surface. The results indicate that the C―O bond length of 0.1161 nm after adsorption at the C-end is elongated compared with the 0.1141 and 0.1136 nm of free and adsorbed on ZrO2. The vibrational frequency of CO at 2018 cm-1 is red-shifted compared with free CO. CO has some positive charge after adsorption and charge transfer is predominantly by the π back-donation bonding mechanism of the Pt 5d→CO 2π orbital.
We studied the adsorption of CO molecules on perfect and Pt-adsorbed t-ZrO2(101) surfaces using a periodic slab model by PW91 of generalized gradient approximation (GGA) within the framework of density functional theory. The results indicated that the second sub-surface oxygen and the second bridge sites are the most stable adsorbed sites for CO and Pt on the ZrO2(101) surface, respectively. When the coverage is 0.25 ML (monolayer) the most stable models were obtained with adsorption energies of 56.2 and 352.7 kJ·mol-1. The most stable model of CO adsorbed on the Pt/t-ZrO2(101) surface was obtained by C-end adsorption with an adsorption energy of 323.8 kJ·mol-1. We considered vibrational frequency calculations, density of states and the Mulliken population of the adsorption systems before and after adsorption and these were compared for CO and Pt adsorption onto the ZrO2 surface. The results indicate that the C―O bond length of 0.1161 nm after adsorption at the C-end is elongated compared with the 0.1141 and 0.1136 nm of free and adsorbed on ZrO2. The vibrational frequency of CO at 2018 cm-1 is red-shifted compared with free CO. CO has some positive charge after adsorption and charge transfer is predominantly by the π back-donation bonding mechanism of the Pt 5d→CO 2π orbital.
2012, 28(01): 58-64
doi: 10.3866/PKU.WHXB20122858
Abstract:
We propose a periodic interaction model for layered double hydroxides, CuZnMgAl quaternary hydrotalcites [(M)-IV-LDHs (M=Cu, Zn, Mg, Al)]. Based on density functional theory the geometries of CuZnMgAl quaternary hydrotalcites were optimized using the CASTEP program. The impacts of the Jahn-Teller effect and the location of chlorine over the layer distortion and stability were investigated by analyzing the geometric parameters, the electronic arrangement, charge populations, binding energies, and hydrogen-bonding. The optimization results showed that the Jahn-Teller effect does not only exist in Cu2+ when its d orbital is partially filled but it also exists in Zn2+ when its d orbital is full as well as in Mg2+ when its p orbital is partially filled. Systems where the chloride is located above the metal show greater metal distortion than systems with anions located above non-metals. Eight systems (Nos. 1-8) were chosen for our work and their absolute binding energy values were found to decrease gradually while the stability of the systems became worse. Finally, the systems became unstable and were found to be flattened octahedral forms. These results help us to better understand the Jahn-Teller effect in copper-containing IV-LDHs from theory.
We propose a periodic interaction model for layered double hydroxides, CuZnMgAl quaternary hydrotalcites [(M)-IV-LDHs (M=Cu, Zn, Mg, Al)]. Based on density functional theory the geometries of CuZnMgAl quaternary hydrotalcites were optimized using the CASTEP program. The impacts of the Jahn-Teller effect and the location of chlorine over the layer distortion and stability were investigated by analyzing the geometric parameters, the electronic arrangement, charge populations, binding energies, and hydrogen-bonding. The optimization results showed that the Jahn-Teller effect does not only exist in Cu2+ when its d orbital is partially filled but it also exists in Zn2+ when its d orbital is full as well as in Mg2+ when its p orbital is partially filled. Systems where the chloride is located above the metal show greater metal distortion than systems with anions located above non-metals. Eight systems (Nos. 1-8) were chosen for our work and their absolute binding energy values were found to decrease gradually while the stability of the systems became worse. Finally, the systems became unstable and were found to be flattened octahedral forms. These results help us to better understand the Jahn-Teller effect in copper-containing IV-LDHs from theory.
2012, 28(01): 65-72
doi: 10.3866/PKU.WHXB20122865
Abstract:
Resonance Raman spectra of N-Methylpyrrole-2-carboxaldehyde (NMPCA) were obtained and seven excitations covered the A- and B-band electronic absorptions. The electronic excitations and the Franck-Condon region structural dynamics of NMPCA were studied by resonance Raman spectroscopy and time-dependent density functional theory (TD-DFT) calculations. The A- and B-band electronic absorptions were assigned to π →π* transitions on the basis of the TD-B3LYP/6-311 ++ G(d,p) level of theory. The resonance Raman spectra showed Raman intensity in the fundamentals, the overtones and the combination bands for about 11-13 vibrational modes (A-band excitation) or 7-11 vibrational modes (B-band excitation). These were predominately due to the C＝O stretch mode ν7, the ring deformation+N1－ C6 stretch ν17, the ring deformation mode ν21 and the C6－N1－C2/C2－C3－C4 anti-symmetry stretch mode ν14. This indicates that the Franck-Condon region Sπ structural dynamics of NMPCA mainly occurs along the C＝O stretch, the ring deformation, and the N1－C6 stretch reaction coordinates. In a certain solvent and under different excitation wavelengths the relative intensity of the C＝O stretch mode ν7 versus the C6－N1－C2/C2－C3 －C4 anti-symmetry stretch mode ν14 shows an intense to weak to intense change as the excitation wavelengths decrease. This intensity variation directly reflects the Sn/Sπ state-mixing or crossing of the potential energy surfaces in the Franck-Condon region. Solvents can efficiently tune the Franck- Condon region Sn/Sπ state-mixing or crossing processes.
Resonance Raman spectra of N-Methylpyrrole-2-carboxaldehyde (NMPCA) were obtained and seven excitations covered the A- and B-band electronic absorptions. The electronic excitations and the Franck-Condon region structural dynamics of NMPCA were studied by resonance Raman spectroscopy and time-dependent density functional theory (TD-DFT) calculations. The A- and B-band electronic absorptions were assigned to π →π* transitions on the basis of the TD-B3LYP/6-311 ++ G(d,p) level of theory. The resonance Raman spectra showed Raman intensity in the fundamentals, the overtones and the combination bands for about 11-13 vibrational modes (A-band excitation) or 7-11 vibrational modes (B-band excitation). These were predominately due to the C＝O stretch mode ν7, the ring deformation+N1－ C6 stretch ν17, the ring deformation mode ν21 and the C6－N1－C2/C2－C3－C4 anti-symmetry stretch mode ν14. This indicates that the Franck-Condon region Sπ structural dynamics of NMPCA mainly occurs along the C＝O stretch, the ring deformation, and the N1－C6 stretch reaction coordinates. In a certain solvent and under different excitation wavelengths the relative intensity of the C＝O stretch mode ν7 versus the C6－N1－C2/C2－C3 －C4 anti-symmetry stretch mode ν14 shows an intense to weak to intense change as the excitation wavelengths decrease. This intensity variation directly reflects the Sn/Sπ state-mixing or crossing of the potential energy surfaces in the Franck-Condon region. Solvents can efficiently tune the Franck- Condon region Sn/Sπ state-mixing or crossing processes.
2012, 28(01): 73-77
doi: 10.3866/PKU.WHXB20122873
Abstract:
The one-electron redox characteristics of one-hydroxyl radical adducts of adenine-thymine base pairs were calculated using density functional theory at the B3LYP/DZP ++//B3LYP/6-31 ++ G(d,p) level. The computational results indicate that all eight adducts are strong oxidizing agents and very weak reducing agents. For the AC2-T, AC4-T, and AC5-T adducts electron capture causes a hydrogen atom migration from the N3 site of thymine to the N1 site of adenine. The hydrogen atom transfer reactions in the anion adducts are attributable to a higher electron density of the adenine moiety. The higher electron density favors the formation of a new N－H bond on the adenine base.
The one-electron redox characteristics of one-hydroxyl radical adducts of adenine-thymine base pairs were calculated using density functional theory at the B3LYP/DZP ++//B3LYP/6-31 ++ G(d,p) level. The computational results indicate that all eight adducts are strong oxidizing agents and very weak reducing agents. For the AC2-T, AC4-T, and AC5-T adducts electron capture causes a hydrogen atom migration from the N3 site of thymine to the N1 site of adenine. The hydrogen atom transfer reactions in the anion adducts are attributable to a higher electron density of the adenine moiety. The higher electron density favors the formation of a new N－H bond on the adenine base.
2012, 28(01): 78-84
doi: 10.3866/PKU.WHXB20122878
Abstract:
The molecular structures, UV-Vis absorption spectra, and energy level structures of the dyes D-SS and D-ST were simulated using density functional theory, time-dependent density functional theory (TDDFT), and natural bond orbital analysis, which provided the physical mechanisms of dye-sensitized solar cells (DSSCs) containing D-ST and D-SS. The UV-Vis absorption spectrum of D-SS showed a significant red shift compared with that of D-ST and the molar absorption coefficient of D-SS was higher than that of D-ST. D-SS molecules should have a higher solar radiation photon-harvesting ability than D-ST molecules, but the energy level of the highest occupied molecular orbital (HOMO) of D-SS was higher than the redox energy level of the electrolyte (I-/I3-). As a result, an optically excited D-SS molecule cannot be successfully recovered by accepting an electron from the electrolyte after being oxidized by injecting an electron towards the TiO2 electrode. This limits the photon harvesting ability of D-SS molecules, and thereby significantly decreases the photovoltaic properties and energy conversion efficiency of DSSCs containing D-SS. This allows the photovoltaic properties of DSSCs containing D-SS to be understood, especially why its photovoltaic energy conversion efficiency is lower than that of DSSCs containing D-ST. The position of the HOMO energy level of dye-sensitized molecules is very important for the operation of DSSCs, and that of the organic sensitizer molecules used in DSSCs must be lower than the redox energy level of the electrolyte.
The molecular structures, UV-Vis absorption spectra, and energy level structures of the dyes D-SS and D-ST were simulated using density functional theory, time-dependent density functional theory (TDDFT), and natural bond orbital analysis, which provided the physical mechanisms of dye-sensitized solar cells (DSSCs) containing D-ST and D-SS. The UV-Vis absorption spectrum of D-SS showed a significant red shift compared with that of D-ST and the molar absorption coefficient of D-SS was higher than that of D-ST. D-SS molecules should have a higher solar radiation photon-harvesting ability than D-ST molecules, but the energy level of the highest occupied molecular orbital (HOMO) of D-SS was higher than the redox energy level of the electrolyte (I-/I3-). As a result, an optically excited D-SS molecule cannot be successfully recovered by accepting an electron from the electrolyte after being oxidized by injecting an electron towards the TiO2 electrode. This limits the photon harvesting ability of D-SS molecules, and thereby significantly decreases the photovoltaic properties and energy conversion efficiency of DSSCs containing D-SS. This allows the photovoltaic properties of DSSCs containing D-SS to be understood, especially why its photovoltaic energy conversion efficiency is lower than that of DSSCs containing D-ST. The position of the HOMO energy level of dye-sensitized molecules is very important for the operation of DSSCs, and that of the organic sensitizer molecules used in DSSCs must be lower than the redox energy level of the electrolyte.
2012, 28(01): 85-89
doi: 10.3866/PKU.WHXB201111153
Abstract:
The influence of intermittent microwave heating (IMH) on the physicochemical and electrochemical properties of platinum loaded on multi-walled carbon nanotubes (Pt/MWCNTs) was investigated. X-ray diffraction results revealed that the crystal size of Pt particles hardly increased for smaller numbers of pulse repetitions, but became much larger as the number of pulse repetitions increased. Cyclic voltammetry (CV) and rotating disk electrode (RDE) results showed that the Pt/MWCNTs catalysts prepared by IMH in a repeated pulse form of 5s-on/5s-off for 20 pulse repetitions possessed the largest electrochemical surface area. An onset potential of approximately 1.0 V (vs RHE) was observed for the oxygen reduction reaction in oxygen-saturated 0.5 mol·L-1 H2SO4 aqueous solutions. The IMH method is simple, economical, and can potentially be scaled up for the mass production of nanomaterials.
The influence of intermittent microwave heating (IMH) on the physicochemical and electrochemical properties of platinum loaded on multi-walled carbon nanotubes (Pt/MWCNTs) was investigated. X-ray diffraction results revealed that the crystal size of Pt particles hardly increased for smaller numbers of pulse repetitions, but became much larger as the number of pulse repetitions increased. Cyclic voltammetry (CV) and rotating disk electrode (RDE) results showed that the Pt/MWCNTs catalysts prepared by IMH in a repeated pulse form of 5s-on/5s-off for 20 pulse repetitions possessed the largest electrochemical surface area. An onset potential of approximately 1.0 V (vs RHE) was observed for the oxygen reduction reaction in oxygen-saturated 0.5 mol·L-1 H2SO4 aqueous solutions. The IMH method is simple, economical, and can potentially be scaled up for the mass production of nanomaterials.
2012, 28(01): 90-94
doi: 10.3866/PKU.WHXB20122890
Abstract:
The choice of fuel is an important issue influencing the selection of catalyst, cost, and commercialization of fuel cells. Electrochemically-active and low-cost fuels that can be oxidized by non-precious catalysts are an attractive objective. The native electrochemical activity and low cost of sulfide make it a suitable candidate. Fuel cells using alkaline sulfide as a fuel were developed. At room temperature, a single cell containing non-precious anode catalysts achieves a maximum power density of 12.3 mW·cm-2 with a current density of 42.8 mA·cm-2. Life tests show that alkaline sulfide fuel cells exhibit od durability. Ion chromatography detected considerable amounts of thiosulfate, sulfite, and sulfate. The deep oxidation and high capacity of sulfide make it an attractive fuel candidate. Compared with other fuels, sulfide has the advantages of being inexpensive, easy to transport, possesses high electrochemical activity, and can be catalyzed by non-precious catalysts.
The choice of fuel is an important issue influencing the selection of catalyst, cost, and commercialization of fuel cells. Electrochemically-active and low-cost fuels that can be oxidized by non-precious catalysts are an attractive objective. The native electrochemical activity and low cost of sulfide make it a suitable candidate. Fuel cells using alkaline sulfide as a fuel were developed. At room temperature, a single cell containing non-precious anode catalysts achieves a maximum power density of 12.3 mW·cm-2 with a current density of 42.8 mA·cm-2. Life tests show that alkaline sulfide fuel cells exhibit od durability. Ion chromatography detected considerable amounts of thiosulfate, sulfite, and sulfate. The deep oxidation and high capacity of sulfide make it an attractive fuel candidate. Compared with other fuels, sulfide has the advantages of being inexpensive, easy to transport, possesses high electrochemical activity, and can be catalyzed by non-precious catalysts.
2012, 28(01): 95-99
doi: 10.3866/PKU.WHXB201111161
Abstract:
Pr1.2Sr0.8NiO4 (PSNO) cathode material for an intermediate-temperature solid oxide fuel cell (IT-SOFC) was synthesized by a glycine-nitrate process. The phase structure of the synthesized powders was characterized by X-ray diffraction (XRD) analysis. The thermal expansion coefficient (TEC) and the electrical conductivity of the sintered PSNO samples were measured. Electrochemical impedance spectroscopy (EIS) measurements of the PSNO materials were carried out using an electrochemical workstation. Single cells based on the Sm0.2Ce0.8O1.9 (SCO) electrolyte were also assembled and tested. The results show that PSNO materials with a K2NiF4-type structure can be obtained by calcining the precursors at temperatures higher than 1050 °C. The sintered PSNO samples have an average TEC of about 12×10-6 K-1 within 200-800 °C, an electrical conductivity of 155 S·cm-1 at 450 °C and an average conduction activation energy of 0.034 eV at 400-800 °C. Electrochemical impedance spectroscopy (EIS) shows that the area specific resistance (ASR) of the PSNO cathode on the SCO electrolyte is 0.37 Ω·cm2 and the ASR of the single Ni-SCO/SCO/PSNO cell is 0.61 Ω·cm2 at 700 ° C. The single Ni-SCO/SCO/ PSNO cell produces a power density of 288 mW·cm-2 and an open circuit voltage of 0.75 V at 800 °C. Preliminary work showed that the PSNO materials may be a potential cathode material for use in IT-SOFC.
Pr1.2Sr0.8NiO4 (PSNO) cathode material for an intermediate-temperature solid oxide fuel cell (IT-SOFC) was synthesized by a glycine-nitrate process. The phase structure of the synthesized powders was characterized by X-ray diffraction (XRD) analysis. The thermal expansion coefficient (TEC) and the electrical conductivity of the sintered PSNO samples were measured. Electrochemical impedance spectroscopy (EIS) measurements of the PSNO materials were carried out using an electrochemical workstation. Single cells based on the Sm0.2Ce0.8O1.9 (SCO) electrolyte were also assembled and tested. The results show that PSNO materials with a K2NiF4-type structure can be obtained by calcining the precursors at temperatures higher than 1050 °C. The sintered PSNO samples have an average TEC of about 12×10-6 K-1 within 200-800 °C, an electrical conductivity of 155 S·cm-1 at 450 °C and an average conduction activation energy of 0.034 eV at 400-800 °C. Electrochemical impedance spectroscopy (EIS) shows that the area specific resistance (ASR) of the PSNO cathode on the SCO electrolyte is 0.37 Ω·cm2 and the ASR of the single Ni-SCO/SCO/PSNO cell is 0.61 Ω·cm2 at 700 ° C. The single Ni-SCO/SCO/ PSNO cell produces a power density of 288 mW·cm-2 and an open circuit voltage of 0.75 V at 800 °C. Preliminary work showed that the PSNO materials may be a potential cathode material for use in IT-SOFC.
2012, 28(01): 100-104
doi: 10.3866/PKU.WHXB201228100
Abstract:
Vanadium modified LiFe0.5Mn0.5PO4/C cathode materials with a nominal composition of (1-x)LiFe0.5Mn0.5PO4-xLi3V2(PO4)3/C (x=0, 0.1, 0.2, 0.25, 1) were prepared by a solid-state reaction using NH4VO3 as the vanadium source. The electrochemical performance of the LiFe0.5Mn0.5PO4-based compounds improved upon vanadium modification. The 0.8LiFe0.5Mn0.5PO4-0.2Li3V2(PO4)3/C (LFMP-LVP/C) sample exhibited the highest discharge capacity of 141 mAh·g-1 at 0.1C rate. X-ray diffraction analyses revealed a dual phase of the LFMP-LVP/C composite with the coexistence of an olivine-type LiFe0.5Mn0.5PO4/C phase and a NASICON-type Li3V2(PO4)3 phase. Energy dispersive X-ray spectroscopy (EDS) analysis indicates a uniform distribution of Fe, Mn, V, and P in the composite. The electronic conductivity of LFMP-LVP was found to be 2.7×10-7 S·cm-1, which is much higher than the value (1.9×10-8 S·cm-1) of LiFe0.5Mn0.5PO4 and similar to the value (2.3 × 10-7 S·cm-1) of pure Li3V2(PO4)3. Vanadium modification remarkably reduced the electrode polarization of the LFMP-LVP/C cathode during the charge-discharge procedure. This suggests that vanadium modification is an effective method to improve the electrochemical performance of olivine-type cathode materials.
Vanadium modified LiFe0.5Mn0.5PO4/C cathode materials with a nominal composition of (1-x)LiFe0.5Mn0.5PO4-xLi3V2(PO4)3/C (x=0, 0.1, 0.2, 0.25, 1) were prepared by a solid-state reaction using NH4VO3 as the vanadium source. The electrochemical performance of the LiFe0.5Mn0.5PO4-based compounds improved upon vanadium modification. The 0.8LiFe0.5Mn0.5PO4-0.2Li3V2(PO4)3/C (LFMP-LVP/C) sample exhibited the highest discharge capacity of 141 mAh·g-1 at 0.1C rate. X-ray diffraction analyses revealed a dual phase of the LFMP-LVP/C composite with the coexistence of an olivine-type LiFe0.5Mn0.5PO4/C phase and a NASICON-type Li3V2(PO4)3 phase. Energy dispersive X-ray spectroscopy (EDS) analysis indicates a uniform distribution of Fe, Mn, V, and P in the composite. The electronic conductivity of LFMP-LVP was found to be 2.7×10-7 S·cm-1, which is much higher than the value (1.9×10-8 S·cm-1) of LiFe0.5Mn0.5PO4 and similar to the value (2.3 × 10-7 S·cm-1) of pure Li3V2(PO4)3. Vanadium modification remarkably reduced the electrode polarization of the LFMP-LVP/C cathode during the charge-discharge procedure. This suggests that vanadium modification is an effective method to improve the electrochemical performance of olivine-type cathode materials.
2012, 28(01): 105-110
doi: 10.3866/PKU.WHXB201228105
Abstract:
Graphene-modified mesoporous LiFePO4 microsphere composites were synthesized by a hydrothermal method and subsequent annealing. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and galvanostatic charge-discharge techniques were used to characterize the morphology, structure and electrochemical performance of the resulting composites. The graphene-modified LiFePO4 microspheres exhibited a high discharge capacity of 141 mAh·g-1 at 1C, and 105 mAh·g-1 at 50C, while LiFePO4/C only delivered 137 mAh·g-1 at 1C, 64 mAh·g-1 at 50C in an aqueous electrolyte of 2 mol·L-1 LiNO3. The graphene-modified LiFePO4 exhibited excellent cyclability compared with LiFePO4/C, with a capacity retention of about 83.7% after 60 cycles versus about 70.2% for LiFePO4/C. The improved electrochemical performance is attributed to the formation of a three-dimensional (3D) graphene network.
Graphene-modified mesoporous LiFePO4 microsphere composites were synthesized by a hydrothermal method and subsequent annealing. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, and galvanostatic charge-discharge techniques were used to characterize the morphology, structure and electrochemical performance of the resulting composites. The graphene-modified LiFePO4 microspheres exhibited a high discharge capacity of 141 mAh·g-1 at 1C, and 105 mAh·g-1 at 50C, while LiFePO4/C only delivered 137 mAh·g-1 at 1C, 64 mAh·g-1 at 50C in an aqueous electrolyte of 2 mol·L-1 LiNO3. The graphene-modified LiFePO4 exhibited excellent cyclability compared with LiFePO4/C, with a capacity retention of about 83.7% after 60 cycles versus about 70.2% for LiFePO4/C. The improved electrochemical performance is attributed to the formation of a three-dimensional (3D) graphene network.
2012, 28(01): 111-120
doi: 10.3866/PKU.WHXB201228111
Abstract:
Nickel and nickel-aluminum alloy were successfully electrodeposited on Cu electrodes from 2: 1 molar ratio aluminum chloride (AlCl3)/triethylamine hydrochloride (Et3NHCl) ionic liquids containing Ni2+ by constant potential electrolysis. The nucleation mechanism of nickel electrodeposition on Cu was investigated by cyclic voltammograms and chronoamperometry. The mechanism and the influence of experimental conditions on the current efficiency and the surface morphology of nickel-aluminum alloy electrodeposition on Cu electrodes were studied. The electrodeposition of nickel on Cu electrodes was controlled by three-dimensional instantaneous nucleation with diffusion-controlled growth. The Ni-Al alloy composition did not become independent of the deposition charge until at least 3.0 C had been accumulated. The mechanism of Ni-Al alloy formation appears to involve the underpotential deposition of aluminum on the developing nickel deposit and alloy formation must be kinetically hindered because the aluminum content is always less than that predicted from theoretical considerations. The Ni-Al alloy that was obtained on the Cu electrode was dense, continuous, and well adherent when the deposition current was small and stationary. If these conditions were not met, a nodule surface morphology appeared. The current efficiency of the Ni-Al alloy electrodeposition was greater than 90% and the deposition composition was close to that of the Ni3Al alloy.
Nickel and nickel-aluminum alloy were successfully electrodeposited on Cu electrodes from 2: 1 molar ratio aluminum chloride (AlCl3)/triethylamine hydrochloride (Et3NHCl) ionic liquids containing Ni2+ by constant potential electrolysis. The nucleation mechanism of nickel electrodeposition on Cu was investigated by cyclic voltammograms and chronoamperometry. The mechanism and the influence of experimental conditions on the current efficiency and the surface morphology of nickel-aluminum alloy electrodeposition on Cu electrodes were studied. The electrodeposition of nickel on Cu electrodes was controlled by three-dimensional instantaneous nucleation with diffusion-controlled growth. The Ni-Al alloy composition did not become independent of the deposition charge until at least 3.0 C had been accumulated. The mechanism of Ni-Al alloy formation appears to involve the underpotential deposition of aluminum on the developing nickel deposit and alloy formation must be kinetically hindered because the aluminum content is always less than that predicted from theoretical considerations. The Ni-Al alloy that was obtained on the Cu electrode was dense, continuous, and well adherent when the deposition current was small and stationary. If these conditions were not met, a nodule surface morphology appeared. The current efficiency of the Ni-Al alloy electrodeposition was greater than 90% and the deposition composition was close to that of the Ni3Al alloy.
2012, 28(01): 121-126
doi: 10.3866/PKU.WHXB201228121
Abstract:
In this paper, the corrosion process of a tinplate in a functional beverage was investigated using electrochemical impedance spectroscope (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), scanning probe microscopy (SPM), and X-ray photoelectron spectroscopy (XPS), and a corrosion mechanism is proposed. We conclude that an increase in the impedance modulus at low frequency is due to the corrosion product forming on the surface of the tinplate over the first 31 h. With an increase in the immersion time a decrease in the impedance modulus at low frequency is due to the detachment of the corrosion product and the corrosion of the carbon steel substrate. X-ray photoelectron spectroscopy (XPS) results show that the corrosion product is mainly composed of a Sn(II)/Sn(IV) citrate complex or an Fe(III) citrate complex. Furthermore, the corrosion product film is first enriched with Sn and then enriched with Fe after immersion in functional beverage for 24 d. We propose that the tinplate is mainly corroded by the organic acids that exist in functional beverages.
In this paper, the corrosion process of a tinplate in a functional beverage was investigated using electrochemical impedance spectroscope (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), scanning probe microscopy (SPM), and X-ray photoelectron spectroscopy (XPS), and a corrosion mechanism is proposed. We conclude that an increase in the impedance modulus at low frequency is due to the corrosion product forming on the surface of the tinplate over the first 31 h. With an increase in the immersion time a decrease in the impedance modulus at low frequency is due to the detachment of the corrosion product and the corrosion of the carbon steel substrate. X-ray photoelectron spectroscopy (XPS) results show that the corrosion product is mainly composed of a Sn(II)/Sn(IV) citrate complex or an Fe(III) citrate complex. Furthermore, the corrosion product film is first enriched with Sn and then enriched with Fe after immersion in functional beverage for 24 d. We propose that the tinplate is mainly corroded by the organic acids that exist in functional beverages.
2012, 28(01): 127-136
doi: 10.3866/PKU.WHXB201111112
Abstract:
The polarization curves of magnesium alloy AZ91D with a micro-arc oxidation (MAO) coating showed several typical patterns caused by differences in the composition and structure of the coating. The pattern of the polarization curve of magnesium alloy AZ91D with a MAO coating depends on the primary composition and structure of the MAO coating and many experimental factors, such as the concentration of chloride ions, pH of the electrolyte, degree of cathodic polarization, and the exposed area of the specimen. These factors change the pattern of polarization curve of magnesium alloy AZ91D with MAO coating by affecting the main composition and structure of the MAO coating because of its instability in aqueous solution. Compositional and structural changes in the MAO coating on magnesium alloy AZ91D were investigated by Fourier transform infrared microscopic mapping and the corresponding optical photographs, respectively. A model was proposed to describe the transformation of the MAO coating in aqueous NaCl solution. For magnesium alloy AZ91D with a MAO coating immersed in NaCl solution, the rate determining steps of the anodic and cathodic reactions are the mass diffusion and charge transfer steps, respectively. As a result, the corrosion current density fitted from the polarization curve is not an accurate corrosion rate.
The polarization curves of magnesium alloy AZ91D with a micro-arc oxidation (MAO) coating showed several typical patterns caused by differences in the composition and structure of the coating. The pattern of the polarization curve of magnesium alloy AZ91D with a MAO coating depends on the primary composition and structure of the MAO coating and many experimental factors, such as the concentration of chloride ions, pH of the electrolyte, degree of cathodic polarization, and the exposed area of the specimen. These factors change the pattern of polarization curve of magnesium alloy AZ91D with MAO coating by affecting the main composition and structure of the MAO coating because of its instability in aqueous solution. Compositional and structural changes in the MAO coating on magnesium alloy AZ91D were investigated by Fourier transform infrared microscopic mapping and the corresponding optical photographs, respectively. A model was proposed to describe the transformation of the MAO coating in aqueous NaCl solution. For magnesium alloy AZ91D with a MAO coating immersed in NaCl solution, the rate determining steps of the anodic and cathodic reactions are the mass diffusion and charge transfer steps, respectively. As a result, the corrosion current density fitted from the polarization curve is not an accurate corrosion rate.
2012, 28(01): 137-145
doi: 10.3866/PKU.WHXB201228137
Abstract:
Cyclic voltammetry and in situ Raman spectroscopy were used to determine the adsorption mechanism of nicotinic acid onto passive iron film surface. Its ability to form a surface complex tends to stabilize the interstitial FeⅡ in FeⅢ states and results in the progressive development of an insoluble film. Furthermore, an analytical investigation using a rotating electrochemical quartz crystal microbalance (rEQCM) showed that the adsorption isotherms of nicotinic acid onto iron in the active and passive states followed Langmuir-Freundlich behavior from which the adsorption constant, standard free energy of adsorption, and heterogeneity could be calculated. The organic molecules attach to the film surface by chemisorption and the interstitial cations are fixed in the octahedral sites giving stable nanocrystals. These assumptions were confirmed by scanning electron microscopy (SEM) and attenuated total reflection transform infrared (ATR FTIR) spectroscopy.
Cyclic voltammetry and in situ Raman spectroscopy were used to determine the adsorption mechanism of nicotinic acid onto passive iron film surface. Its ability to form a surface complex tends to stabilize the interstitial FeⅡ in FeⅢ states and results in the progressive development of an insoluble film. Furthermore, an analytical investigation using a rotating electrochemical quartz crystal microbalance (rEQCM) showed that the adsorption isotherms of nicotinic acid onto iron in the active and passive states followed Langmuir-Freundlich behavior from which the adsorption constant, standard free energy of adsorption, and heterogeneity could be calculated. The organic molecules attach to the film surface by chemisorption and the interstitial cations are fixed in the octahedral sites giving stable nanocrystals. These assumptions were confirmed by scanning electron microscopy (SEM) and attenuated total reflection transform infrared (ATR FTIR) spectroscopy.
2012, 28(01): 146-153
doi: 10.3866/PKU.WHXB201228146
Abstract:
In this paper, ultra-low interfacial tension was obtained in realistic oil-water systems using ion pair surfactant systems. To improve the solubility of the ion pair surfactants, polyoxyethylene chain was introduced into the anionic surfactant molecular structure, and a three-component strategy where ion pair surfactants were combined with a non-ionic surfactant was used. Furthermore, the effects of the structures of the cationic and non-ionic surfactants, distribution ratio of the three components, and surfactant concentration on oil-water interfacial tension were studied. We successfully achieved the ultra-low interfacial tension in the Shengli oil fields using the mixed systems combining ion pairs and non-ionic agents. Several systems possessed an interfacial tension as low as 10-4 mN·m-1. Because of the strong electrostatic attraction between surfactant ions, our systems possess ultra-low interfacial tension after adsorption. The results show that after 48 h quartz adsorption, the systems can still reduce the interfacial tension to an ultra-low level.
In this paper, ultra-low interfacial tension was obtained in realistic oil-water systems using ion pair surfactant systems. To improve the solubility of the ion pair surfactants, polyoxyethylene chain was introduced into the anionic surfactant molecular structure, and a three-component strategy where ion pair surfactants were combined with a non-ionic surfactant was used. Furthermore, the effects of the structures of the cationic and non-ionic surfactants, distribution ratio of the three components, and surfactant concentration on oil-water interfacial tension were studied. We successfully achieved the ultra-low interfacial tension in the Shengli oil fields using the mixed systems combining ion pairs and non-ionic agents. Several systems possessed an interfacial tension as low as 10-4 mN·m-1. Because of the strong electrostatic attraction between surfactant ions, our systems possess ultra-low interfacial tension after adsorption. The results show that after 48 h quartz adsorption, the systems can still reduce the interfacial tension to an ultra-low level.
2012, 28(01): 154-160
doi: 10.3866/PKU.WHXB201228154
Abstract:
C-doped TiO2 was prepared from butyl titanate and glucose by a hydrothermal method. The prepared C-doped TiO2 was further modified with Ag@AgCl. The obtained samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), BET surface area analysis, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of the samples was evaluated by the degradation of methyl orange and phenol under the visible light irradiation (λ >420 nm). After modification with Ag@AgCl, the C-doped TiO2 samples had a larger particle size and smaller surface area with enhanced response to visible light and greatly improved visible-light photocatalytic activity. The degradation rates of methyl orange and phenol over Ag@AgCl/TiO2-xCx were 5.5 and 3.4 times as large as those over TiO2-xCx, respectively. The photocatalytic activity of Ag@AgCl/TiO2-xCx under visible light remained almost unchanged after three cycles.
C-doped TiO2 was prepared from butyl titanate and glucose by a hydrothermal method. The prepared C-doped TiO2 was further modified with Ag@AgCl. The obtained samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), BET surface area analysis, and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of the samples was evaluated by the degradation of methyl orange and phenol under the visible light irradiation (λ >420 nm). After modification with Ag@AgCl, the C-doped TiO2 samples had a larger particle size and smaller surface area with enhanced response to visible light and greatly improved visible-light photocatalytic activity. The degradation rates of methyl orange and phenol over Ag@AgCl/TiO2-xCx were 5.5 and 3.4 times as large as those over TiO2-xCx, respectively. The photocatalytic activity of Ag@AgCl/TiO2-xCx under visible light remained almost unchanged after three cycles.
2012, 28(01): 161-169
doi: 10.3866/PKU.WHXB201228161
Abstract:
A yellow N-F co-doped TiO2 photocatalyst (TiONF) exhibited high activity over a wide light spectrum range and a multipore structure was prepared by a hydrolysis-precipitation method using an ionic liquid ([Bmim]PF6)-water mixture as the solvent and TiCl4 as the precursor. Photocatalytic activity was investigated by the photocatalytic degradation of phenol under ultraviolet (UV), artificial visible (Vis), and solar light irradiation. X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), spectroscopy, and N2 adsorption-desorption were used for catalyst characterization. The results show that TiONF synthesis in an ionic liquid-water mixture solvent with suitable N-F doping gives high activity under UV, Vis, and solar light irradiation, and the activities are higher than those obtained by synthesis in pure water. The ionic liquid-water mixture solvent leads to N and F being incorporated into the TiO2 lattice and N-F co-doping can increase the amount of surface OH- on TiO2. The new bandgap formed by N-F doping can induce a second adsorption edge (450-530 nm), which can be excited by Vis irradiation and induce Vis activity. N-F co-doping retards the phase transformation. In addition, an ionic liquid-water mixture as a solvent benefits the dispersion of TiO2, increases the SBET and reduces the particle size.
A yellow N-F co-doped TiO2 photocatalyst (TiONF) exhibited high activity over a wide light spectrum range and a multipore structure was prepared by a hydrolysis-precipitation method using an ionic liquid ([Bmim]PF6)-water mixture as the solvent and TiCl4 as the precursor. Photocatalytic activity was investigated by the photocatalytic degradation of phenol under ultraviolet (UV), artificial visible (Vis), and solar light irradiation. X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), spectroscopy, and N2 adsorption-desorption were used for catalyst characterization. The results show that TiONF synthesis in an ionic liquid-water mixture solvent with suitable N-F doping gives high activity under UV, Vis, and solar light irradiation, and the activities are higher than those obtained by synthesis in pure water. The ionic liquid-water mixture solvent leads to N and F being incorporated into the TiO2 lattice and N-F co-doping can increase the amount of surface OH- on TiO2. The new bandgap formed by N-F doping can induce a second adsorption edge (450-530 nm), which can be excited by Vis irradiation and induce Vis activity. N-F co-doping retards the phase transformation. In addition, an ionic liquid-water mixture as a solvent benefits the dispersion of TiO2, increases the SBET and reduces the particle size.
2012, 28(01): 170-176
doi: 10.3866/PKU.WHXB201228170
Abstract:
CuO-ZnO-ZrO2 (CZZ) catalysts for methanol synthesis from CO2 hydrogenation were prepared by a citric acid combustion method. The combustion reactions were analyzed in terms of propellant chemistry and the combustion behavior was recorded by thermo-gravimetric/differential thermal analysis (TG-DTA). The as-prepared CZZ powders were investigated with X-ray diffraction (XRD), N2 adsorption, temperature-programmed reduction (TPR), and reactive N2O adsorption techniques and the catalytic activities were evaluated for methanol synthesis from CO2 hydrogenation. The results show that the influence of citric acid quantity on the physicochemical and catalytic properties of CZZ is subtle, and the reason is related to the characteristics of the combustion reaction. Furthermore, the relationship between the quantity of fuel (citric acid, urea, and glycine) and the properties of the catalysts was determined. The citric acid combustion method exhibits better controllability and it is a simple, fast, and valuable route for the preparation of the CZZ catalyst for methanol synthesis from CO2 hydrogenation.
CuO-ZnO-ZrO2 (CZZ) catalysts for methanol synthesis from CO2 hydrogenation were prepared by a citric acid combustion method. The combustion reactions were analyzed in terms of propellant chemistry and the combustion behavior was recorded by thermo-gravimetric/differential thermal analysis (TG-DTA). The as-prepared CZZ powders were investigated with X-ray diffraction (XRD), N2 adsorption, temperature-programmed reduction (TPR), and reactive N2O adsorption techniques and the catalytic activities were evaluated for methanol synthesis from CO2 hydrogenation. The results show that the influence of citric acid quantity on the physicochemical and catalytic properties of CZZ is subtle, and the reason is related to the characteristics of the combustion reaction. Furthermore, the relationship between the quantity of fuel (citric acid, urea, and glycine) and the properties of the catalysts was determined. The citric acid combustion method exhibits better controllability and it is a simple, fast, and valuable route for the preparation of the CZZ catalyst for methanol synthesis from CO2 hydrogenation.
2012, 28(01): 177-183
doi: 10.3866/PKU.WHXB201111181
Abstract:
Activated carbon (AC) was modified by supercritical methanol (scCH3OH) treatment, HNO3 oxidation, and HNO3 oxidation in combination with scCH3OH treatment. The pristine and modified AC samples were characterized by N2 physisorption, Boehm titration, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and transmission electron microscopy (TEM). These modifications did not significantly change the surface area and the pore size distribution of the AC. scCH3OH treatment decreased the density of surface acidic groups, especially carboxylic groups. However, HNO3 oxidation increased the density of surface acidic groups. ICP analysis revealed that the ScCH3OH modified sample had a similar adsorptive capacity for ruthenium as the original AC, while the AC oxidized with HNO3 had the highest adsorptive capacity of all samples tested. Ru/AC catalysts were prepared with RuCl3 solution impregnation on the four aforementioned AC supports. The as-prepared catalysts were characterized by TEM, XPS and examined for their effectiveness in D-glucose hydrogenation as well. The modifications drastically affected the properties of the activated carbons and the catalysts loaded on them. The dispersion of ruthenium after impregnation was highly dependent on the density of surface acidic groups. The AC sample treated by scCH3OH, which contained a lower amount of surface acidic complexes, showed the highest dispersion of ruthenium. The XPS results showed that the scCH3OH modification enhanced the interaction between AC and Ru. The Ru/AC-scCH3OH catalyst showed the highest activity for hydrogenation of D-glucose; producing a reaction rate 1.56 times higher than that produced by Ru/AC.
Activated carbon (AC) was modified by supercritical methanol (scCH3OH) treatment, HNO3 oxidation, and HNO3 oxidation in combination with scCH3OH treatment. The pristine and modified AC samples were characterized by N2 physisorption, Boehm titration, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and transmission electron microscopy (TEM). These modifications did not significantly change the surface area and the pore size distribution of the AC. scCH3OH treatment decreased the density of surface acidic groups, especially carboxylic groups. However, HNO3 oxidation increased the density of surface acidic groups. ICP analysis revealed that the ScCH3OH modified sample had a similar adsorptive capacity for ruthenium as the original AC, while the AC oxidized with HNO3 had the highest adsorptive capacity of all samples tested. Ru/AC catalysts were prepared with RuCl3 solution impregnation on the four aforementioned AC supports. The as-prepared catalysts were characterized by TEM, XPS and examined for their effectiveness in D-glucose hydrogenation as well. The modifications drastically affected the properties of the activated carbons and the catalysts loaded on them. The dispersion of ruthenium after impregnation was highly dependent on the density of surface acidic groups. The AC sample treated by scCH3OH, which contained a lower amount of surface acidic complexes, showed the highest dispersion of ruthenium. The XPS results showed that the scCH3OH modification enhanced the interaction between AC and Ru. The Ru/AC-scCH3OH catalyst showed the highest activity for hydrogenation of D-glucose; producing a reaction rate 1.56 times higher than that produced by Ru/AC.
2012, 28(01): 184-188
doi: 10.3866/PKU.WHXB201111162
Abstract:
α-Fe2O3 samples with nanocube and nanorod morphologies were synthesized by a simple hydrothermal route. The samples were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), temperature- programmed reduction by H2 (H2-TPR), and temperature-programmed desorption of NO (NO-TPD), and tested for the selective catalytic reduction with NH3 (NH3-SCR) of NO at moderate temperatures. The α-Fe2O3 nanocubes possessed predominantly exposed {012} faces with low surface energy, while the nanorods also had some high energy {110} faces exposed. The catalytic activities of the α-Fe2O3 samples were predominantly verned by their surface structures. The nanorods showed much higher activity than the nanocubes under identical conditions, consistent with the better redox properties of the nanorods as confirmed by H2-TPR and NO-TPD measurements. Therefore, α-Fe2O3 nanorods with exposed high energy faces have much higher activity for NH3-SCR than nanocubes with exposed low energy faces under identical reaction conditions.
α-Fe2O3 samples with nanocube and nanorod morphologies were synthesized by a simple hydrothermal route. The samples were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), temperature- programmed reduction by H2 (H2-TPR), and temperature-programmed desorption of NO (NO-TPD), and tested for the selective catalytic reduction with NH3 (NH3-SCR) of NO at moderate temperatures. The α-Fe2O3 nanocubes possessed predominantly exposed {012} faces with low surface energy, while the nanorods also had some high energy {110} faces exposed. The catalytic activities of the α-Fe2O3 samples were predominantly verned by their surface structures. The nanorods showed much higher activity than the nanocubes under identical conditions, consistent with the better redox properties of the nanorods as confirmed by H2-TPR and NO-TPD measurements. Therefore, α-Fe2O3 nanorods with exposed high energy faces have much higher activity for NH3-SCR than nanocubes with exposed low energy faces under identical reaction conditions.
2012, 28(01): 189-194
doi: 10.3866/PKU.WHXB201111152
Abstract:
This paper presents a comprehensive study about the adsorption ability of five different sites in metal-organic framework (MOF-5), including pure and different groups (―NO2, ―NH2, ―CH3, ― OZn) decorated ones, for CO2 and other greenhouse gases and industrial waste gases. The selective adsorption ability was investigated based on the tight binding approximation method. The results show that sites I and II are the major adsorption sites for pure MOF-5. The highest adsorption energy can be -0.25 eV. Group decoration enhances the adsorption ability of MOF-5 when adsorbing CO2, which is highly related to the activity of decorated groups and the local configurations. Among these groups, ― NO2 enhances the adsorption ability of all sites for CO2 absorption. The ―NO2 decorated MOF-5 shows an obvious selective adsorption ability for different gases in the air environment (O2, N2, H2O, CO2) and for industrial waste gases environment (CO2, CO, NO, NO2, SO2, SO3).
This paper presents a comprehensive study about the adsorption ability of five different sites in metal-organic framework (MOF-5), including pure and different groups (―NO2, ―NH2, ―CH3, ― OZn) decorated ones, for CO2 and other greenhouse gases and industrial waste gases. The selective adsorption ability was investigated based on the tight binding approximation method. The results show that sites I and II are the major adsorption sites for pure MOF-5. The highest adsorption energy can be -0.25 eV. Group decoration enhances the adsorption ability of MOF-5 when adsorbing CO2, which is highly related to the activity of decorated groups and the local configurations. Among these groups, ― NO2 enhances the adsorption ability of all sites for CO2 absorption. The ―NO2 decorated MOF-5 shows an obvious selective adsorption ability for different gases in the air environment (O2, N2, H2O, CO2) and for industrial waste gases environment (CO2, CO, NO, NO2, SO2, SO3).
2012, 28(01): 195-200
doi: 10.3866/PKU.WHXB201228195
Abstract:
Various amine-functionalized CO2 adsorbents were prepared by incorporating tetraethylenepenthamine (TEPA) onto SBA-15(P) by controlling the impregnation method and its process. The materials were characterized using X-ray diffraction (XRD), N2-adsorption, elemental analysis, and Fourier transform infrared (FTIR) techniques. Their adsorptive capacities were determined by CO2-temperature programmed desorption (TPD). The results indicate that the dynamic impregnation process using a TEPA ethanol solution was successful in loading TEPA into the channels of SBA-15(P). Moreover, bonding formation between the highly dispersed TEPA and SBA-15(P) was facilitated to CO2 adsorption/desorption. Therefore, a binding mechanism is proposed. The －NH2 group of TEPA forms hydrogen bonds with －OH and C－O－C groups on SBA-15(P), which results in the better dispersion of TEPA. However, the dynamic impregnation process for the TEPA ethanol solution can effectively avoid the formation of hydrogen bonds between the intra- and inter-molecules resulting in the high adsorptive capacity of the amino groups in TEPA.
Various amine-functionalized CO2 adsorbents were prepared by incorporating tetraethylenepenthamine (TEPA) onto SBA-15(P) by controlling the impregnation method and its process. The materials were characterized using X-ray diffraction (XRD), N2-adsorption, elemental analysis, and Fourier transform infrared (FTIR) techniques. Their adsorptive capacities were determined by CO2-temperature programmed desorption (TPD). The results indicate that the dynamic impregnation process using a TEPA ethanol solution was successful in loading TEPA into the channels of SBA-15(P). Moreover, bonding formation between the highly dispersed TEPA and SBA-15(P) was facilitated to CO2 adsorption/desorption. Therefore, a binding mechanism is proposed. The －NH2 group of TEPA forms hydrogen bonds with －OH and C－O－C groups on SBA-15(P), which results in the better dispersion of TEPA. However, the dynamic impregnation process for the TEPA ethanol solution can effectively avoid the formation of hydrogen bonds between the intra- and inter-molecules resulting in the high adsorptive capacity of the amino groups in TEPA.
2012, 28(01): 201-207
doi: 10.3866/PKU.WHXB201228201
Abstract:
The adsorption of surfactants on mineral surface has a great influence on the solid hydrophobicity and flotation behavior. The relationship between the hydrocarbon tail length of the primary alkylamines and muscovite hydrophobicity was investigated by contact angle measurement, atomic force microscopy (AFM), density functional theory (DFT), and molecular dynamics (MD) simulation. By comparing the oxygen density and the hydrogen bonds number profile, we observed that the formed hydrogen bonds for each water molecule on the interface between hydrocarbon tails and the water phase were fewer than that in the bulk. Additionally, the muscovite that absorbed alkylamines transformed from a hydrophilic surface to hydrophobic one. We also found that the octadecylamine (ODA)-absorbed muscovite surface was more hydrophobic than the dodecylamine (DDA)-absorbed surface while they were both in a monolayer state. Furthermore, because octadecylamine has a much lower hemi-micelle concentration (HMC) than dodecylamine, it forms multilayer more easily, meaning that the primary alkylamine with longer hydrocarbon tail is a better choice for the hydrophobicity enhancement of muscovite surface. The experimental results are in od agreement with theoretical calculations.
The adsorption of surfactants on mineral surface has a great influence on the solid hydrophobicity and flotation behavior. The relationship between the hydrocarbon tail length of the primary alkylamines and muscovite hydrophobicity was investigated by contact angle measurement, atomic force microscopy (AFM), density functional theory (DFT), and molecular dynamics (MD) simulation. By comparing the oxygen density and the hydrogen bonds number profile, we observed that the formed hydrogen bonds for each water molecule on the interface between hydrocarbon tails and the water phase were fewer than that in the bulk. Additionally, the muscovite that absorbed alkylamines transformed from a hydrophilic surface to hydrophobic one. We also found that the octadecylamine (ODA)-absorbed muscovite surface was more hydrophobic than the dodecylamine (DDA)-absorbed surface while they were both in a monolayer state. Furthermore, because octadecylamine has a much lower hemi-micelle concentration (HMC) than dodecylamine, it forms multilayer more easily, meaning that the primary alkylamine with longer hydrocarbon tail is a better choice for the hydrophobicity enhancement of muscovite surface. The experimental results are in od agreement with theoretical calculations.
2012, 28(01): 208-212
doi: 10.3866/PKU.WHXB201228208
Abstract:
Four kinds of CdS quantum dots (Qds) with four different surface-capping organic groups were prepared by a colloidal chemical method. The linear and nonlinear optical properties of the materials were characterized using transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) spectroscopy, and Z-scan measurements. The results show that the particle size, the surface morphology, and the defect concentration are the main factors that determine the nonlinear optical properties.
Four kinds of CdS quantum dots (Qds) with four different surface-capping organic groups were prepared by a colloidal chemical method. The linear and nonlinear optical properties of the materials were characterized using transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence (PL) spectroscopy, and Z-scan measurements. The results show that the particle size, the surface morphology, and the defect concentration are the main factors that determine the nonlinear optical properties.
2012, 28(01): 213-216
doi: 10.3866/PKU.WHXB201228213
Abstract:
Laser flash photolysis was used to study the photosensitized oxidation mechanism of vitamin K3, commonly known as 2-methyl-1,4-naphthoquinone (MQ), with tryptophan (TrpH) or tyrosine (TyrOH) in acetonitrile/water (1:1, V/V) solution. The triplet state of MQ reacted with TrpH or TyrOH by electron transfer with the formation of a MQ anion radical, which was directly observed in the transient absorption spectrum. The rate constants of the electron transfer reactions were determined to be 1.1×109 and 0.6×109 L·mol-1·s-1 for TrpH and TyrOH, respectively. The free energy changes (ΔG) of the reactions showed that the proposed electron transfer steps are thermodynamically feasible.
Laser flash photolysis was used to study the photosensitized oxidation mechanism of vitamin K3, commonly known as 2-methyl-1,4-naphthoquinone (MQ), with tryptophan (TrpH) or tyrosine (TyrOH) in acetonitrile/water (1:1, V/V) solution. The triplet state of MQ reacted with TrpH or TyrOH by electron transfer with the formation of a MQ anion radical, which was directly observed in the transient absorption spectrum. The rate constants of the electron transfer reactions were determined to be 1.1×109 and 0.6×109 L·mol-1·s-1 for TrpH and TyrOH, respectively. The free energy changes (ΔG) of the reactions showed that the proposed electron transfer steps are thermodynamically feasible.
2012, 28(01): 217-222
doi: 10.3866/PKU.WHXB201111111
Abstract:
The ferroelectric thin film of lead magnesium niobate-lead titanate (PMN-PT) was fabricated and characterized using UV-Vis transmission spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). To determine the photocurrent properties of the bulk heterojunction organic blend film a photovoltaic device with the structure of tin indium oxide (ITO)/PMN-PT/organic blend film/aluminum (Al) was fabricated. Under modulated laser irradiation the amplitude and polarity of the transient photocurrent varied with the bias voltage, which shows that the photocurrent polarity of a conventional bulk heterojunction organic photovoltaic device is determined by the internal electric field that is induced by the difference between the work function of the anode and cathode electrodes. A new method is proposed for investigating the photocurrent properties of bulk heterojunction organic photovoltaic devices.
The ferroelectric thin film of lead magnesium niobate-lead titanate (PMN-PT) was fabricated and characterized using UV-Vis transmission spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). To determine the photocurrent properties of the bulk heterojunction organic blend film a photovoltaic device with the structure of tin indium oxide (ITO)/PMN-PT/organic blend film/aluminum (Al) was fabricated. Under modulated laser irradiation the amplitude and polarity of the transient photocurrent varied with the bias voltage, which shows that the photocurrent polarity of a conventional bulk heterojunction organic photovoltaic device is determined by the internal electric field that is induced by the difference between the work function of the anode and cathode electrodes. A new method is proposed for investigating the photocurrent properties of bulk heterojunction organic photovoltaic devices.
2012, 28(01): 223-231
doi: 10.3866/PKU.WHXB201111171
Abstract:
Benzoic acid (BA) was bonded to the side chains of polysulfone (PSF) via a polymer reaction, giving aryl carboxylic acid-functionalized polysulfone (PSFBA). The binary complex PSFBA-Tb(III) and ternary complex PSFBA-Tb(III)-phenanthroline (Phen) were prepared by the coordination of Tb(III) to PSFBA using PSFBA as a macromolecular ligand and Phen as a smaller ligand. The chemical structures of the complexes were characterized by Fourier transform infrared (FTIR) and UV absorption spectroscopies. The relationships between the structure and properties, including the fluorescence emission properties, of the complexes in solution and films were investigated, as well as their thermal stability. All of the polymerrare earth complexes containing PSFBA exhibited very strong characteristic fluorescence emission from Tb(III), namely, BA bonded to the side chains of PSFBA can effectively sensitize Tb(III). The apparent saturated coordination number of PSFBA-Tb(III) is 10, which implies that the coordination of BA to Tb(III) reaches saturation and maximum fluorescence is achieved for the complex PSF-(BA)5-Tb(III). The ternary complex PSF-(BA)5-Tb(III)-(Phen)1, which is prepared by adding Phen to a solution of PSF-(BA)5-Tb(III), possesses the strongest fluorescence emission and excellent thermal stability compared with ternary complexes PSF-(BA)1-Tb(III)-(Phen)3 and PSF-(BA)1-Tb(III)-(Phen)2, which were prepared using the conventional ratios of reagents.
Benzoic acid (BA) was bonded to the side chains of polysulfone (PSF) via a polymer reaction, giving aryl carboxylic acid-functionalized polysulfone (PSFBA). The binary complex PSFBA-Tb(III) and ternary complex PSFBA-Tb(III)-phenanthroline (Phen) were prepared by the coordination of Tb(III) to PSFBA using PSFBA as a macromolecular ligand and Phen as a smaller ligand. The chemical structures of the complexes were characterized by Fourier transform infrared (FTIR) and UV absorption spectroscopies. The relationships between the structure and properties, including the fluorescence emission properties, of the complexes in solution and films were investigated, as well as their thermal stability. All of the polymerrare earth complexes containing PSFBA exhibited very strong characteristic fluorescence emission from Tb(III), namely, BA bonded to the side chains of PSFBA can effectively sensitize Tb(III). The apparent saturated coordination number of PSFBA-Tb(III) is 10, which implies that the coordination of BA to Tb(III) reaches saturation and maximum fluorescence is achieved for the complex PSF-(BA)5-Tb(III). The ternary complex PSF-(BA)5-Tb(III)-(Phen)1, which is prepared by adding Phen to a solution of PSF-(BA)5-Tb(III), possesses the strongest fluorescence emission and excellent thermal stability compared with ternary complexes PSF-(BA)1-Tb(III)-(Phen)3 and PSF-(BA)1-Tb(III)-(Phen)2, which were prepared using the conventional ratios of reagents.
2012, 28(01): 232-238
doi: 10.3866/PKU.WHXB201111151
Abstract:
CdTe/CdSe core/shell quantum dots (QDs) with different numbers of CdSe layers were synthesized in aqueous media by sequentially adding freshly-prepared solutions of NaHSe and CdCl2 to a solution of CdTe QDs several times. The optical properties and microstructures of the resulting QDs were investigated. Compared with those of CdTe QDs, the optical absorption and fluorescence emission peaks of CdTe/CdSe core/shell QDs with a single CdSe layer shifted to longer wavelength. As the number of CdSe layers was increased, the optical absorption spectra of the CdTe/CdSe core/shell QDs covered a wider range and extended to longer wavelengths, the intensity of fluorescence emission decreased gradually, and the fluorescence lifetime increased significantly, consistent with the behavior of type II core/ shell QDs. Compared with those of CdTe/CdSe QDs with a single CdSe layer, the diffraction peaks of the CdTe/CdSe QDs with three CdSe layers shifted from the standard positions of CdTe diffraction peaks to those of CdSe. The CdTe/CdSe type II core/shell QDs show promise for application in solar cells because of their broad absorption spectra that extend to longer wavelengths.
CdTe/CdSe core/shell quantum dots (QDs) with different numbers of CdSe layers were synthesized in aqueous media by sequentially adding freshly-prepared solutions of NaHSe and CdCl2 to a solution of CdTe QDs several times. The optical properties and microstructures of the resulting QDs were investigated. Compared with those of CdTe QDs, the optical absorption and fluorescence emission peaks of CdTe/CdSe core/shell QDs with a single CdSe layer shifted to longer wavelength. As the number of CdSe layers was increased, the optical absorption spectra of the CdTe/CdSe core/shell QDs covered a wider range and extended to longer wavelengths, the intensity of fluorescence emission decreased gradually, and the fluorescence lifetime increased significantly, consistent with the behavior of type II core/ shell QDs. Compared with those of CdTe/CdSe QDs with a single CdSe layer, the diffraction peaks of the CdTe/CdSe QDs with three CdSe layers shifted from the standard positions of CdTe diffraction peaks to those of CdSe. The CdTe/CdSe type II core/shell QDs show promise for application in solar cells because of their broad absorption spectra that extend to longer wavelengths.
2012, 28(01): 239-244
doi: 10.3866/PKU.WHXB201228239
Abstract:
A self-healing pure SiC coating was prepared on a carbon/carbon (C/C) composite by a two-step technique to protect the C/C composite from oxidation. First, SiC nanowires were obtained on the substrate surface by the thermal decomposition of hydrogen silicone oil (H-PSO). Second, a coating with a thickness of 100-200 μm was produced by infiltrating with silicon at high temperature in an ar n atmosphere. The morphology and phase composition of the coating were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Oxidation tests were carried out on specimens and the results indicated that the obtained coating consisted of pure SiC and had a certain self-healing ability. The SiC self-healing coating significantly increased the antioxidant properties of the C/C composites and it protected the C/C composites from oxidation at 1400 °C in air over 4 h with a corresponding mass loss of only 0.71%.
A self-healing pure SiC coating was prepared on a carbon/carbon (C/C) composite by a two-step technique to protect the C/C composite from oxidation. First, SiC nanowires were obtained on the substrate surface by the thermal decomposition of hydrogen silicone oil (H-PSO). Second, a coating with a thickness of 100-200 μm was produced by infiltrating with silicon at high temperature in an ar n atmosphere. The morphology and phase composition of the coating were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Oxidation tests were carried out on specimens and the results indicated that the obtained coating consisted of pure SiC and had a certain self-healing ability. The SiC self-healing coating significantly increased the antioxidant properties of the C/C composites and it protected the C/C composites from oxidation at 1400 °C in air over 4 h with a corresponding mass loss of only 0.71%.
2012, 28(01): 245-250
doi: 10.3866/PKU.WHXB201228245
Abstract:
A CeO2-ZrO2-Al2O3 composite oxide (CZA) and a CeO2-ZrO2 composite oxide (CZ) were prepared by the co-precipitation method. The samples were thermally aged in a flowing air atmosphere and in 10% H2/Ar flow. The structure and performance of the composite oxides were studied by X-ray diffraction (XRD), oxygen storage capacity (OSC) measurements, and H2 temperature-programmed reduction (H2- TPR). The results show that a CeAlO3 phase was formed after CZA was reductively aged at 950 °C and an increase in temperature benefited the formation of CeAlO3. The OSC of CZA increased with an increase in the reductive treatment temperature and it was 1270.3 μmol·g-1 when the temperature reached 900 °C. However, the OSC decreased with an increase in the temperature. After CZA was reduced at 1100 °C the OSC was only 23.2 μmol·g-1. We found that the OSC and the reducibility of the material were remarkably influenced by the formation of a CeAlO3 phase after CZA was reductively aged.
A CeO2-ZrO2-Al2O3 composite oxide (CZA) and a CeO2-ZrO2 composite oxide (CZ) were prepared by the co-precipitation method. The samples were thermally aged in a flowing air atmosphere and in 10% H2/Ar flow. The structure and performance of the composite oxides were studied by X-ray diffraction (XRD), oxygen storage capacity (OSC) measurements, and H2 temperature-programmed reduction (H2- TPR). The results show that a CeAlO3 phase was formed after CZA was reductively aged at 950 °C and an increase in temperature benefited the formation of CeAlO3. The OSC of CZA increased with an increase in the reductive treatment temperature and it was 1270.3 μmol·g-1 when the temperature reached 900 °C. However, the OSC decreased with an increase in the temperature. After CZA was reduced at 1100 °C the OSC was only 23.2 μmol·g-1. We found that the OSC and the reducibility of the material were remarkably influenced by the formation of a CeAlO3 phase after CZA was reductively aged.
2012, 28(01): 251-256
doi: 10.3866/PKU.WHXB201228251
Abstract:
Thin hybrid films of ZnO/eosin-Y were prepared by electrodeposition at -0.8 and -0.9 V in aqueous and non-aqueous baths at temperatures ranging from 40 to 90 °C with dye concentrations of 100 and 400 μmol·L-1. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and absorption spectroscopy. The films prepared in a non-aqueous bath were non-porous and did not adsorb dye molecules on their surface. However, the films grown in aqueous media were porous in nature and adsorbed dye during the deposition of ZnO. Preferential growth of the film along the (002) face was observed, and the highest crystallinity was achieved when the film was deposited at 60 °C. The maximum absorption was achieved for the films grown at 60 to 70 °C, a deposition potential of -0.9 V, and a dye concentration of 100 μmol·L-1.
Thin hybrid films of ZnO/eosin-Y were prepared by electrodeposition at -0.8 and -0.9 V in aqueous and non-aqueous baths at temperatures ranging from 40 to 90 °C with dye concentrations of 100 and 400 μmol·L-1. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and absorption spectroscopy. The films prepared in a non-aqueous bath were non-porous and did not adsorb dye molecules on their surface. However, the films grown in aqueous media were porous in nature and adsorbed dye during the deposition of ZnO. Preferential growth of the film along the (002) face was observed, and the highest crystallinity was achieved when the film was deposited at 60 °C. The maximum absorption was achieved for the films grown at 60 to 70 °C, a deposition potential of -0.9 V, and a dye concentration of 100 μmol·L-1.
