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2017 Volume 38 Issue 10
2017, 38(10):
Abstract:
2017, 38(10): 1659-1663
doi: 10.1016/S1872-2067(17)62894-8
Abstract:
2017, 38(10): 1664-1667
doi: 10.1016/S1872-2067(17)62901-2
Abstract:
An iodine-catalyzed sulfenylation of pyrazoles at room temperature is described, in which a variety of pyrazoles were well tolerated and the desired products were obtained in good to excellent yields.
An iodine-catalyzed sulfenylation of pyrazoles at room temperature is described, in which a variety of pyrazoles were well tolerated and the desired products were obtained in good to excellent yields.
2017, 38(10): 1668-1679
doi: 10.1016/S1872-2067(17)62885-7
Abstract:
Efficient, cost-effective electrocatalysts for an oxygen reduction reaction (ORR) are currently required for fuel cells. In the present work, riboflavin was used as a cheap, nontoxic carbon and nitrogen precursor to prepare Fe-N-C catalysts via one-step pyrolysis in the presence of anhydrous iron chloride. Raman spectroscopy indicated that the catalyst containing nitrogen created a great quantity of defects in the carbon structures, while nitrogen adsorption-desorption isotherms showed that the catalyst was mesoporous. Transmission electron microscopy demonstrated that the Fe-N-C catalyst was composed of very thin, curved and porous graphene layers together with some Fe2O3 nanoparticles, and X-ray diffraction patterns confirmed that the carbon in the catalyst was highly graphitized. X-ray photoelectron spectroscopy indicated that the active sites for the ORR were primarily composed of graphitic nitrogen, although Fe sites also played an important role. The ORR activity of the Fe-N-C catalyst reached a maximum of 4.16 mA cm-2, and its chronoamperometric response was found to decrease by only 3% after operating for 3 h at 0.66 V (vs RHE) in an O2-saturated 0.1 mol L-1 KOH solution. In contrast, a commercial 40 wt% Pt/C catalyst with a loading of 0.2 mgPt cm-2 exhibited an activity of 4.46 mA cm-2 and a 40% loss of response. The electrochemical performance of this new Fe-N-C catalyst was therefore comparable to that of the Pt/C catalyst while showing significantly better stability.
Efficient, cost-effective electrocatalysts for an oxygen reduction reaction (ORR) are currently required for fuel cells. In the present work, riboflavin was used as a cheap, nontoxic carbon and nitrogen precursor to prepare Fe-N-C catalysts via one-step pyrolysis in the presence of anhydrous iron chloride. Raman spectroscopy indicated that the catalyst containing nitrogen created a great quantity of defects in the carbon structures, while nitrogen adsorption-desorption isotherms showed that the catalyst was mesoporous. Transmission electron microscopy demonstrated that the Fe-N-C catalyst was composed of very thin, curved and porous graphene layers together with some Fe2O3 nanoparticles, and X-ray diffraction patterns confirmed that the carbon in the catalyst was highly graphitized. X-ray photoelectron spectroscopy indicated that the active sites for the ORR were primarily composed of graphitic nitrogen, although Fe sites also played an important role. The ORR activity of the Fe-N-C catalyst reached a maximum of 4.16 mA cm-2, and its chronoamperometric response was found to decrease by only 3% after operating for 3 h at 0.66 V (vs RHE) in an O2-saturated 0.1 mol L-1 KOH solution. In contrast, a commercial 40 wt% Pt/C catalyst with a loading of 0.2 mgPt cm-2 exhibited an activity of 4.46 mA cm-2 and a 40% loss of response. The electrochemical performance of this new Fe-N-C catalyst was therefore comparable to that of the Pt/C catalyst while showing significantly better stability.
2017, 38(10): 1680-1687
doi: 10.1016/S1872-2067(17)62876-6
Abstract:
A Pt/graphene-TiO2 catalyst was prepared by a microwave-assisted solvothermal method and was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, and linear sweep voltammetry. The cubic TiO2 particles were approximately 60 nm in size and were distributed on the graphene sheets. The Pt nanoparticles were uniformly distributed between the TiO2 particles and the graphene sheet. The catalyst exhibited a significant improvement in activity and stability towards the oxygen reduction reaction compared with Pt/C, which resulted from the high electronic conductivity of graphene and strong metal-support interactions.
A Pt/graphene-TiO2 catalyst was prepared by a microwave-assisted solvothermal method and was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, and linear sweep voltammetry. The cubic TiO2 particles were approximately 60 nm in size and were distributed on the graphene sheets. The Pt nanoparticles were uniformly distributed between the TiO2 particles and the graphene sheet. The catalyst exhibited a significant improvement in activity and stability towards the oxygen reduction reaction compared with Pt/C, which resulted from the high electronic conductivity of graphene and strong metal-support interactions.
2017, 38(10): 1688-1696
doi: 10.1016/S1872-2067(17)62893-6
Abstract:
Mixed phase TiO2 photocatalysts doped with C and Y were synthesized by a sol-gel process. The effects of C and Y doping and annealing temperatures on the structural and optical properties, and photocatalytic activity were investigated. We found that both C and Y doping can broaden the absorption spectrum of TiO2 to the visible light region and inhibit recombination of photogenerated electron/hole pairs. The incorporation of Y into the TiO2 lattice inhibited growth of crystalline grains, which increased the specific surface area and enhanced the photocatalytic activity. The photocatalytic performance of the samples was investigated in the photocatalytic degradation of methyl blue under visible light irradiation. The rate of methyl blue degradation over the (C, Y)-co-doped TiO2 sample was much higher than those of undoped TiO2, C-TiO2, and Y-TiO2. Additionally, the apparent first-order rate constant of the co-doped sample was 3.5 times as large as that of undoped mix phase TiO2 under the same experimental conditions. The enhanced photocatalytic activity can be attributed to the synergic effect of (C, Y)-co-doping and the formation of an appropriate crystalline structure.
Mixed phase TiO2 photocatalysts doped with C and Y were synthesized by a sol-gel process. The effects of C and Y doping and annealing temperatures on the structural and optical properties, and photocatalytic activity were investigated. We found that both C and Y doping can broaden the absorption spectrum of TiO2 to the visible light region and inhibit recombination of photogenerated electron/hole pairs. The incorporation of Y into the TiO2 lattice inhibited growth of crystalline grains, which increased the specific surface area and enhanced the photocatalytic activity. The photocatalytic performance of the samples was investigated in the photocatalytic degradation of methyl blue under visible light irradiation. The rate of methyl blue degradation over the (C, Y)-co-doped TiO2 sample was much higher than those of undoped TiO2, C-TiO2, and Y-TiO2. Additionally, the apparent first-order rate constant of the co-doped sample was 3.5 times as large as that of undoped mix phase TiO2 under the same experimental conditions. The enhanced photocatalytic activity can be attributed to the synergic effect of (C, Y)-co-doping and the formation of an appropriate crystalline structure.
2017, 38(10): 1697-1710
doi: 10.1016/S1872-2067(17)62891-2
Abstract:
Glycerol dehydration to acrolein over a series of supported silicotungstic acid catalysts (SiWx-Al/Zry) was investigated. Characterization results showed that the final catalyst had high thermal stability, a large pore diameter, strong Lewis acidic sites, and a large specific surface area. X-ray photoelectron survey spectra clearly showed peaks attributable to W (W 4f = 35.8 eV), Al2O3 (Al 2p = 74.9 eV), and ZrO2 (Zr 3d = 182.8 eV). The highest acrolein selectivity achieved was 87.3% at 97% glycerol conversion over the SiW20-Al/Zr10 catalyst. The prepared catalysts were highly active and selective for acrolein formation even after 40 h because of the presence of high concentrations of Lewis acidic sites, which significantly reduced the amount of coke on the catalyst surface. Response surface methodology optimization showed that 87.7% acrolein selectivity at 97.0% glycerol conversion could be obtained under the following optimal reaction conditions: 0.5 wt% catalyst, reaction temperature 300 ℃, and feed glycerol concentration 10 wt%. Evaluation of a mass-transfer-limited regime showed the absence of internal and external diffusions over pellets of diameter dP<20 μm. These results show that glycerol dehydration over a strong Lewis acid catalyst is a promising method for acrolein production.
Glycerol dehydration to acrolein over a series of supported silicotungstic acid catalysts (SiWx-Al/Zry) was investigated. Characterization results showed that the final catalyst had high thermal stability, a large pore diameter, strong Lewis acidic sites, and a large specific surface area. X-ray photoelectron survey spectra clearly showed peaks attributable to W (W 4f = 35.8 eV), Al2O3 (Al 2p = 74.9 eV), and ZrO2 (Zr 3d = 182.8 eV). The highest acrolein selectivity achieved was 87.3% at 97% glycerol conversion over the SiW20-Al/Zr10 catalyst. The prepared catalysts were highly active and selective for acrolein formation even after 40 h because of the presence of high concentrations of Lewis acidic sites, which significantly reduced the amount of coke on the catalyst surface. Response surface methodology optimization showed that 87.7% acrolein selectivity at 97.0% glycerol conversion could be obtained under the following optimal reaction conditions: 0.5 wt% catalyst, reaction temperature 300 ℃, and feed glycerol concentration 10 wt%. Evaluation of a mass-transfer-limited regime showed the absence of internal and external diffusions over pellets of diameter dP<20 μm. These results show that glycerol dehydration over a strong Lewis acid catalyst is a promising method for acrolein production.
2017, 38(10): 1711-1718
doi: 10.1016/S1872-2067(17)62907-3
Abstract:
Graphitic carbon nitride (g-C3N4) nanosheet photocatalysts were synthesized via a facile impregnation-thermal method. The as-prepared materials were characterized and investigated as metal-free photocatalysts for the degradation of phenol in aqueous solution under visible light. Results revealed that the g-C3N4 nanosheets exhibited a 78.9% degradation for phenol after 30 min, which was much faster than that of the pristine g-C3N4. Using Brunauer-Emmett-Teller theory, the surface area of g-C3N4 nanosheets was 103.24 m2/g, which was much larger than that of g-C3N4. The larger surface area increases the contact area of the material with phenol, enhancing the photocatalytic activity. These results highlight the potential application of sustainable metal-free photocatalysts in water purification.
Graphitic carbon nitride (g-C3N4) nanosheet photocatalysts were synthesized via a facile impregnation-thermal method. The as-prepared materials were characterized and investigated as metal-free photocatalysts for the degradation of phenol in aqueous solution under visible light. Results revealed that the g-C3N4 nanosheets exhibited a 78.9% degradation for phenol after 30 min, which was much faster than that of the pristine g-C3N4. Using Brunauer-Emmett-Teller theory, the surface area of g-C3N4 nanosheets was 103.24 m2/g, which was much larger than that of g-C3N4. The larger surface area increases the contact area of the material with phenol, enhancing the photocatalytic activity. These results highlight the potential application of sustainable metal-free photocatalysts in water purification.
2017, 38(10): 1719-1725
doi: 10.1016/S1872-2067(17)62884-5
Abstract:
A novel-structured Mo-Cu-Fe-O composite was successfully prepared by co-precipitation and impregnation method. The properties of the as-prepared samples were determined using X-ray diffraction, temperature-programmed reduction by H2, cyclic voltammetry, and temperature-programmed desorption by O2. The results showed that Mo6+ diffused into the Cu-Fe-O crystal lattice and then formed a new crystalline phase of CuMoO4. The Mo-Cu-Fe-O catalyst had redox properties, and its surface contained active sites for oxygen adsorption. In addition, the catalytic activity of the Mo-Cu-Fe-O composite was evaluated by the degradation of Cationic Red GTL, Crystal Violet, and Acid Red in catalytic wet air oxidation (CWAO) at ambient temperature and pressure. The Mo-Cu-Fe-O catalyst showed excellent activity at basic conditions for the degradation of Cationic Red GTL. High removal efficiencies of 91.5% and 92.8% were achieved for Cationic Red GTL and Crystal Violet, respectively, in wastewater, and the efficiency remained high after seven cycles. However, almost no degradation of Acid Red occurred in the CWAO process. Furthermore, hydroxyl radicals were formed in the CWAO process, which induced the decomposition of the two cationic dyes in wastewater, and the toxicity of their effluents was decreased after degradation. The results indicate that the Mo-Cu-Fe-O composite shows excellent catalytic activity for the treatment of wastewater contaminated with cationic dyes.
A novel-structured Mo-Cu-Fe-O composite was successfully prepared by co-precipitation and impregnation method. The properties of the as-prepared samples were determined using X-ray diffraction, temperature-programmed reduction by H2, cyclic voltammetry, and temperature-programmed desorption by O2. The results showed that Mo6+ diffused into the Cu-Fe-O crystal lattice and then formed a new crystalline phase of CuMoO4. The Mo-Cu-Fe-O catalyst had redox properties, and its surface contained active sites for oxygen adsorption. In addition, the catalytic activity of the Mo-Cu-Fe-O composite was evaluated by the degradation of Cationic Red GTL, Crystal Violet, and Acid Red in catalytic wet air oxidation (CWAO) at ambient temperature and pressure. The Mo-Cu-Fe-O catalyst showed excellent activity at basic conditions for the degradation of Cationic Red GTL. High removal efficiencies of 91.5% and 92.8% were achieved for Cationic Red GTL and Crystal Violet, respectively, in wastewater, and the efficiency remained high after seven cycles. However, almost no degradation of Acid Red occurred in the CWAO process. Furthermore, hydroxyl radicals were formed in the CWAO process, which induced the decomposition of the two cationic dyes in wastewater, and the toxicity of their effluents was decreased after degradation. The results indicate that the Mo-Cu-Fe-O composite shows excellent catalytic activity for the treatment of wastewater contaminated with cationic dyes.
2017, 38(10): 1726-1735
doi: 10.1016/S1872-2067(17)62902-4
Abstract:
A novel plasmonic photo-Fenton catalyst of Ag/AgCl/Fe-S was synthesized by ion exchange and photoreduction methods. The obtained catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope imaging, and Brunauer-Emmett-Teller measurements. Moreover, the photocatalytic activity of Ag/AgCl/Fe-S was investigated for its degradation activity towards bisphenol A (BPA) as target pollutant under visible light irradiation. The effects of H2O2 concentration, pH value, illumination intensity, and catalyst dosage on BPA degradation were examined. Our results indicated that the Ag/AgCl material was successfully loaded onto Fe-sepiolite and showed a high photocatalytic activity under illumination by visible light. Furthermore, active species capture experiments were performed to explore the photocatalytic mechanism of the Ag/AgCl/Fe-S in this heterogeneous photo-Fenton process, where the major active species included hydroxyl radicals (·OH) and holes (h+).
A novel plasmonic photo-Fenton catalyst of Ag/AgCl/Fe-S was synthesized by ion exchange and photoreduction methods. The obtained catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope imaging, and Brunauer-Emmett-Teller measurements. Moreover, the photocatalytic activity of Ag/AgCl/Fe-S was investigated for its degradation activity towards bisphenol A (BPA) as target pollutant under visible light irradiation. The effects of H2O2 concentration, pH value, illumination intensity, and catalyst dosage on BPA degradation were examined. Our results indicated that the Ag/AgCl material was successfully loaded onto Fe-sepiolite and showed a high photocatalytic activity under illumination by visible light. Furthermore, active species capture experiments were performed to explore the photocatalytic mechanism of the Ag/AgCl/Fe-S in this heterogeneous photo-Fenton process, where the major active species included hydroxyl radicals (·OH) and holes (h+).
2017, 38(10): 1736-1748
doi: 10.1016/S1872-2067(17)62883-3
Abstract:
The influence of the magnetism of transition metal oxide, nickel(Ⅱ) oxide (NiO), on its surface reactivity and the dependence of surface reactivity on surface orientation and reactant magnetism were studied by density functional theory plus U calculations. We considered five different antiferromagnetically ordered structures and one ferromagnetically ordered structure, NiO(001) and Ni(011) surfaces, paramagnetic molecule NO, and nonparamagnetic molecule CO. The calculations showed that the dependence of surface energies on magnetism was modest, ranging from 49 to 54 meV/Å2 for NiO(001) and from 162 to 172 meV/Å2 for NiO(011). On NiO(001), both molecules preferred the top site of the Ni cation exclusively for all NiO magnetic structures considered, and calculated adsorption energies ranged from -0.33 to -0.37 eV for CO and from -0.42 to -0.46 eV for NO. On NiO(011), both molecules preferred the bridge site of two Ni cations irrespective of the NiO magnetism. It was found that rather than the long-range magnetism of bulk NiO, the local magnetic order of two coordinated Ni cations binding to the adsorbed molecule had a pronounced influence on adsorption. The calculated NO adsorption energy at the (↑↓) bridge sites ranged from -0.99 to -1.05 eV, and become stronger at the (↑↑) bridge sites with values of -1.21 to -1.30 eV. For CO, although the calculated adsorption energies at the (↑↓) bridge sites (-0.73 to -0.75 eV) were very close to those at the (↑↑) bridge sites (-0.71 to -0.72 eV), their electron hybridizations were very different. The present work highlights the importance of the local magnetic order of transition metal oxides on molecular adsorption at multi-fold sites.
The influence of the magnetism of transition metal oxide, nickel(Ⅱ) oxide (NiO), on its surface reactivity and the dependence of surface reactivity on surface orientation and reactant magnetism were studied by density functional theory plus U calculations. We considered five different antiferromagnetically ordered structures and one ferromagnetically ordered structure, NiO(001) and Ni(011) surfaces, paramagnetic molecule NO, and nonparamagnetic molecule CO. The calculations showed that the dependence of surface energies on magnetism was modest, ranging from 49 to 54 meV/Å2 for NiO(001) and from 162 to 172 meV/Å2 for NiO(011). On NiO(001), both molecules preferred the top site of the Ni cation exclusively for all NiO magnetic structures considered, and calculated adsorption energies ranged from -0.33 to -0.37 eV for CO and from -0.42 to -0.46 eV for NO. On NiO(011), both molecules preferred the bridge site of two Ni cations irrespective of the NiO magnetism. It was found that rather than the long-range magnetism of bulk NiO, the local magnetic order of two coordinated Ni cations binding to the adsorbed molecule had a pronounced influence on adsorption. The calculated NO adsorption energy at the (↑↓) bridge sites ranged from -0.99 to -1.05 eV, and become stronger at the (↑↑) bridge sites with values of -1.21 to -1.30 eV. For CO, although the calculated adsorption energies at the (↑↓) bridge sites (-0.73 to -0.75 eV) were very close to those at the (↑↑) bridge sites (-0.71 to -0.72 eV), their electron hybridizations were very different. The present work highlights the importance of the local magnetic order of transition metal oxides on molecular adsorption at multi-fold sites.
2017, 38(10): 1749-1758
doi: 10.1016/S1872-2067(17)62887-0
Abstract:
The influence of tungsten trioxide (WO3) loading on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia (NH3) over WO3/cerium dioxide (CeO2) was investigated. The NO conversion first rose and then declined with increasing WO3 loading. It was found that the crystalline WO3 in the 1.6WO3/CeO2 sample could be removed in 25 wt% ammonium hydroxide at 70 ℃, which improved the catalytic activity of the sample. The obtained samples were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, hydrogen (H2) temperature programmed reduction, NH3 temperature programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The results revealed that the dispersed WO3 promoted the catalytic activity of WO3/CeO2 while the crystalline WO3 inhibited catalytic activity. The oxygen activation of CeO2 was inhibited by the coverage of WO3, which weakened NO oxidation and adsorption of nitrate species over WO3/CeO2. In addition, the NH3 adsorption performance on CeO2 was improved by modification with WO3. NH3 was the most stable adsorbed species under NH3 SCR reaction conditions. In situ DRIFT spectra suggested that the NH3 SCR reaction proceeded via the Eley-Rideal mechanism over WO3/CeO2. Thus, when the loading of WO3 was close to the dispersion capacity, the effects of NH3 adsorption and activation were maximized to promote the reaction via the Eley-Rideal route.
The influence of tungsten trioxide (WO3) loading on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia (NH3) over WO3/cerium dioxide (CeO2) was investigated. The NO conversion first rose and then declined with increasing WO3 loading. It was found that the crystalline WO3 in the 1.6WO3/CeO2 sample could be removed in 25 wt% ammonium hydroxide at 70 ℃, which improved the catalytic activity of the sample. The obtained samples were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, hydrogen (H2) temperature programmed reduction, NH3 temperature programmed desorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The results revealed that the dispersed WO3 promoted the catalytic activity of WO3/CeO2 while the crystalline WO3 inhibited catalytic activity. The oxygen activation of CeO2 was inhibited by the coverage of WO3, which weakened NO oxidation and adsorption of nitrate species over WO3/CeO2. In addition, the NH3 adsorption performance on CeO2 was improved by modification with WO3. NH3 was the most stable adsorbed species under NH3 SCR reaction conditions. In situ DRIFT spectra suggested that the NH3 SCR reaction proceeded via the Eley-Rideal mechanism over WO3/CeO2. Thus, when the loading of WO3 was close to the dispersion capacity, the effects of NH3 adsorption and activation were maximized to promote the reaction via the Eley-Rideal route.
2017, 38(10): 1759-1769
doi: 10.1016/S1872-2067(17)62890-0
Abstract:
To reduce energy costs, minimize secondary pollution from undecomposed ozone, and improve the efficiency of ozone use, a novel process of cycled storage-ozone catalytic oxidation (OZCO) was employed to remove formaldehyde (HCHO) at low concentrations in air. We applied Al2O3-supported manganese oxide (MnOx) catalysts to this process, and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts. Owing to the high dispersion of MnOx and low oxidation state of manganese, the MnOx/Al2O3 catalysts with a manganese acetate precursor and 10%-Mn loading showed good performance in both storage and OZCO stages. The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage; however, high relative humidity (RH) favored complete conversion of stored HCHO to CO2 at the OZCO stage and contributed to an excellent carbon balance. Four low concentration HCHO storage-OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3 catalyst at room temperature and a RH of 50%, demonstrating that the proposed storage-OZCO process is an economical, reliable, and promising technique for indoor air purification.
To reduce energy costs, minimize secondary pollution from undecomposed ozone, and improve the efficiency of ozone use, a novel process of cycled storage-ozone catalytic oxidation (OZCO) was employed to remove formaldehyde (HCHO) at low concentrations in air. We applied Al2O3-supported manganese oxide (MnOx) catalysts to this process, and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts. Owing to the high dispersion of MnOx and low oxidation state of manganese, the MnOx/Al2O3 catalysts with a manganese acetate precursor and 10%-Mn loading showed good performance in both storage and OZCO stages. The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage; however, high relative humidity (RH) favored complete conversion of stored HCHO to CO2 at the OZCO stage and contributed to an excellent carbon balance. Four low concentration HCHO storage-OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3 catalyst at room temperature and a RH of 50%, demonstrating that the proposed storage-OZCO process is an economical, reliable, and promising technique for indoor air purification.
2017, 38(10): 1770-1779
doi: 10.1016/S1872-2067(17)62888-2
Abstract:
We report the fabrication and photocatalytic property of a composite of C/CaFe2O4 nanorods (NRs) in an effort to reveal the influence of carbon modification. It is demonstrated that the photocatalytic degradation activity is dependent on the mass ratio of C to CaFe2O4. The optimal carbon content is determined to be 58 wt% to yield a methylene blue (MB) degradation rate of 0.0058 min-1, which is 4.8 times higher than that of the pristine CaFe2O4 NRs. The decoration of carbon on the surface of CaFe2O4 NRs improves its adsorption capacity of the MB dye, which is specifically adsorbed on the surface as a monolayer according to the adsorption isotherm analysis. The trapping experiments of the reactive species indicate that superoxide radicals (·O2-) are the main active species responsible for the removal of MB under visible-light irradiation. Overall, the unique feature of carbon coating enables the efficient separation and transfer of photogenerated electrons and holes, strengthens the adsorption capacity of MB, and improves the light harvesting capability, hence enhancing the overall photocatalytic degradation of MB.
We report the fabrication and photocatalytic property of a composite of C/CaFe2O4 nanorods (NRs) in an effort to reveal the influence of carbon modification. It is demonstrated that the photocatalytic degradation activity is dependent on the mass ratio of C to CaFe2O4. The optimal carbon content is determined to be 58 wt% to yield a methylene blue (MB) degradation rate of 0.0058 min-1, which is 4.8 times higher than that of the pristine CaFe2O4 NRs. The decoration of carbon on the surface of CaFe2O4 NRs improves its adsorption capacity of the MB dye, which is specifically adsorbed on the surface as a monolayer according to the adsorption isotherm analysis. The trapping experiments of the reactive species indicate that superoxide radicals (·O2-) are the main active species responsible for the removal of MB under visible-light irradiation. Overall, the unique feature of carbon coating enables the efficient separation and transfer of photogenerated electrons and holes, strengthens the adsorption capacity of MB, and improves the light harvesting capability, hence enhancing the overall photocatalytic degradation of MB.
