Login In
2023 Volume 39 Issue 5
2023, 39(5): 785-793
doi: 10.11862/CJIC.2023.062
Abstract:
In this work, vertical graphene (VG) and boron-doped vertical graphene (BVG), nitrogen-doped vertical graphene (NVG), and B-N co-doped vertical graphene (BNVG) films were prepared by electron-assisted hot-filament chemical vapor deposition. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to characterize the morphology, microstructure, and composition, and the electrochemical performance of the skin-sensing electrode was analyzed by electrochemical methods. The results show that the BNVG film has a three-dimensional porous network structure, which is formed by interlacing many vertically grown graphene nanosheets. The content of B and N atoms (atomic fraction) in these nanosheets reached 3.78% and 2.75%, respectively. Furthermore, the skin-contact resistance of the BNVG film electrode was only 4.5 kΩ, which was lower than that of the VG electrode. The BNVG film electrode-based sensor had a wide linear range of 0.001 to 10 000 μmol·L-1, and the detection limit was as low as 0.03 μmol·L-1 (S/N=3). Moreover, the developed sensing electrode showed excellent anti-interference ability and long-term stability (45 d).
In this work, vertical graphene (VG) and boron-doped vertical graphene (BVG), nitrogen-doped vertical graphene (NVG), and B-N co-doped vertical graphene (BNVG) films were prepared by electron-assisted hot-filament chemical vapor deposition. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to characterize the morphology, microstructure, and composition, and the electrochemical performance of the skin-sensing electrode was analyzed by electrochemical methods. The results show that the BNVG film has a three-dimensional porous network structure, which is formed by interlacing many vertically grown graphene nanosheets. The content of B and N atoms (atomic fraction) in these nanosheets reached 3.78% and 2.75%, respectively. Furthermore, the skin-contact resistance of the BNVG film electrode was only 4.5 kΩ, which was lower than that of the VG electrode. The BNVG film electrode-based sensor had a wide linear range of 0.001 to 10 000 μmol·L-1, and the detection limit was as low as 0.03 μmol·L-1 (S/N=3). Moreover, the developed sensing electrode showed excellent anti-interference ability and long-term stability (45 d).
2023, 39(5): 794-804
doi: 10.11862/CJIC.2023.058
Abstract:
To study the nucleation, growth, and aggregation of calcium oxalate (CaC2O4) crystals, and to explore the inhibitory effect of degraded Poria cocos polysaccharide (PCP), CaC2O4 crystals formed under different conditions were characterized by X-ray diffraction, FT-IR, scanning electron microscope, Raman spectroscopy, ζ potentiometer, and UV spectrophotometer. The results showed that calcium oxalate monohydrate (COM) crystals were mainly formed at low supersaturation (RS ≤ 26.6). At RS being 37.6 and 46.0, 11.6% and 38.3% calcium oxalate dihydrate (COD) crystals were formed respectively, and the aggregation degree of the crystals increased at high RS. At the same RS, the proportion of COD in the crystal increased with the increase of the Ca2+/Ox2- stoichiometric ratio (nCa2+/nCa2-, Ox2-=C2O42-). The addition of degraded PCP could increase the concentration of soluble Ca2+ ions in the system, reduce the quality of generated CaC2O4 crystals, and increase the absolute value of ζ potential on the crystal surface, all of which are beneficial to inhibit the formation of CaC2O4 stones. Thus, the risk of high Ox2- concentration on the formation of kidney stones is much greater than that of high Ca2+ concentration, suggesting that the risk of oxalic acid intake on CaC2O4 stones is much greater than that of calcium intake. PCP can simultaneously inhibit the nucleation, growth, and aggregation of CaC2O4 crystals.
To study the nucleation, growth, and aggregation of calcium oxalate (CaC2O4) crystals, and to explore the inhibitory effect of degraded Poria cocos polysaccharide (PCP), CaC2O4 crystals formed under different conditions were characterized by X-ray diffraction, FT-IR, scanning electron microscope, Raman spectroscopy, ζ potentiometer, and UV spectrophotometer. The results showed that calcium oxalate monohydrate (COM) crystals were mainly formed at low supersaturation (RS ≤ 26.6). At RS being 37.6 and 46.0, 11.6% and 38.3% calcium oxalate dihydrate (COD) crystals were formed respectively, and the aggregation degree of the crystals increased at high RS. At the same RS, the proportion of COD in the crystal increased with the increase of the Ca2+/Ox2- stoichiometric ratio (nCa2+/nCa2-, Ox2-=C2O42-). The addition of degraded PCP could increase the concentration of soluble Ca2+ ions in the system, reduce the quality of generated CaC2O4 crystals, and increase the absolute value of ζ potential on the crystal surface, all of which are beneficial to inhibit the formation of CaC2O4 stones. Thus, the risk of high Ox2- concentration on the formation of kidney stones is much greater than that of high Ca2+ concentration, suggesting that the risk of oxalic acid intake on CaC2O4 stones is much greater than that of calcium intake. PCP can simultaneously inhibit the nucleation, growth, and aggregation of CaC2O4 crystals.
2023, 39(5): 805-814
doi: 10.11862/CJIC.2023.051
Abstract:
Zirconium-based metal-organic framework and bismuth molybdate composite (MOF-808/Bi2MoO6) was prepared by a simple two-step hydrothermal method. The phase composition, microstructure, optical properties, and photogenerated charge recombination efficiency of the materials were analyzed by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV visible diffuse reflectance spectroscopy, N2 adsorption-desorption testing, and electrochemical testing. Compared with pure Bi2MoO6 and MOF-808, the 0.5%-MOF-808/Bi2MoO6 composite exhibited higher photocatalytic activity, and the degradation rate of the antibiotic ciprofloxacin (CIP) reached 89.7% under visible light irradiation for 120 min. Through radical trapping experiments, it was proved that •O2- was the main active species, based on which we proposed a possible photocatalytic degradation mechanism.
Zirconium-based metal-organic framework and bismuth molybdate composite (MOF-808/Bi2MoO6) was prepared by a simple two-step hydrothermal method. The phase composition, microstructure, optical properties, and photogenerated charge recombination efficiency of the materials were analyzed by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV visible diffuse reflectance spectroscopy, N2 adsorption-desorption testing, and electrochemical testing. Compared with pure Bi2MoO6 and MOF-808, the 0.5%-MOF-808/Bi2MoO6 composite exhibited higher photocatalytic activity, and the degradation rate of the antibiotic ciprofloxacin (CIP) reached 89.7% under visible light irradiation for 120 min. Through radical trapping experiments, it was proved that •O2- was the main active species, based on which we proposed a possible photocatalytic degradation mechanism.
2023, 39(5): 815-829
doi: 10.11862/CJIC.2023.043
Abstract:
Herein, aluminum chloride was used as the aluminum source to modify diatomite (De) by hydrothermal method. Copper hexacyanoferrate (KCuHCF) nanoparticles were loaded onto the surface of modified De by the impregnation method, and two composite adsorbents, γ-AlOOH/De-KCuHCF and γ-Al2O3/De-KCuHCF, were prepared. The prepared materials were characterized and used for Cs+ adsorption. The results showed that the prepared adsorbents had better adsorption performance for Cs+. The maximum adsorption capacity can reach 75.44 and 84.02 mg·g-1, respectively. The desorption rate of γ-Al2O3/De-KCuHCF can reach 81.88% after three consecutive desorption with 3 mol·L-1 NH4NO3 as the desorption solution and the Cs+ adsorption rate of γ-Al2O3/De-KCuHCF in simulated brines was as high as 97.55%. After five adsorption-desorption cycles the adsorption capacity remained high. The adsorption kinetic process and adsorption isotherm model of the prepared adsorbent were also analyzed. The results showed that the adsorption process was in line with the quasi-second-order kinetic model, which was controlled by the intra-particle diffusion and liquid film diffusion, and was in line with the Langmuir adsorption isotherm model.
Herein, aluminum chloride was used as the aluminum source to modify diatomite (De) by hydrothermal method. Copper hexacyanoferrate (KCuHCF) nanoparticles were loaded onto the surface of modified De by the impregnation method, and two composite adsorbents, γ-AlOOH/De-KCuHCF and γ-Al2O3/De-KCuHCF, were prepared. The prepared materials were characterized and used for Cs+ adsorption. The results showed that the prepared adsorbents had better adsorption performance for Cs+. The maximum adsorption capacity can reach 75.44 and 84.02 mg·g-1, respectively. The desorption rate of γ-Al2O3/De-KCuHCF can reach 81.88% after three consecutive desorption with 3 mol·L-1 NH4NO3 as the desorption solution and the Cs+ adsorption rate of γ-Al2O3/De-KCuHCF in simulated brines was as high as 97.55%. After five adsorption-desorption cycles the adsorption capacity remained high. The adsorption kinetic process and adsorption isotherm model of the prepared adsorbent were also analyzed. The results showed that the adsorption process was in line with the quasi-second-order kinetic model, which was controlled by the intra-particle diffusion and liquid film diffusion, and was in line with the Langmuir adsorption isotherm model.
2023, 39(5): 830-840
doi: 10.11862/CJIC.2023.046
Abstract:
The polyhedral structure of Zn-MOF (MOF: metal-organic framework) was synthesized by the coordination of zinc nitrate hexahydrate and 2-methylimidazole. The Zn-MOF was calcined at high temperatures in a nitrogen atmosphere to prepare nanoporous carbon materials. In the process of preparation of flower-like MoS2 by solvothermal reaction, the Zn-MOF-derived nanoporous carbon was introduced and combined with flower-like MoS2 through self-assembly to prepare flower-like Zn-MOF-derived carbon@MoS2 composite absorbing material with regular and ordered structure. A series of characterization and performance tests were carried out to study the physical properties and absorbing properties of the composites. The particle size of polyhedral Zn-MOF-derived nanoporous carbon was 80 nm and encased in 1 μm flower-like MoS2. With the increase of the amount of Zn-MOF-derived carbon, the electromagnetic wave absorption performance of the flower-like Zn-MOF-derived carbon@MoS2 composites firstly increased and then decreased. Based on the high porosity and large specific surface area of Zn-MOF-derived porous carbon and the flower-like structure of MoS2, the electromagnetic wave was reflected and scattered many times, and there was a strong polarization effect, good impedance matching, and synergistic effect between MoS2 and Zn-MOF-derived carbon. When the additional amount (mass fraction) of flower-like Zn-MOF-derived carbon@MoS2 in paraffin was 25%, the frequency was 9.28 GHz, the matching thickness was 3 mm, and the effective absorption bandwidth was 3.04 GHz, the optimal reflection loss reached -49.68 dB, showing excellent electromagnetic wave absorption performance.
The polyhedral structure of Zn-MOF (MOF: metal-organic framework) was synthesized by the coordination of zinc nitrate hexahydrate and 2-methylimidazole. The Zn-MOF was calcined at high temperatures in a nitrogen atmosphere to prepare nanoporous carbon materials. In the process of preparation of flower-like MoS2 by solvothermal reaction, the Zn-MOF-derived nanoporous carbon was introduced and combined with flower-like MoS2 through self-assembly to prepare flower-like Zn-MOF-derived carbon@MoS2 composite absorbing material with regular and ordered structure. A series of characterization and performance tests were carried out to study the physical properties and absorbing properties of the composites. The particle size of polyhedral Zn-MOF-derived nanoporous carbon was 80 nm and encased in 1 μm flower-like MoS2. With the increase of the amount of Zn-MOF-derived carbon, the electromagnetic wave absorption performance of the flower-like Zn-MOF-derived carbon@MoS2 composites firstly increased and then decreased. Based on the high porosity and large specific surface area of Zn-MOF-derived porous carbon and the flower-like structure of MoS2, the electromagnetic wave was reflected and scattered many times, and there was a strong polarization effect, good impedance matching, and synergistic effect between MoS2 and Zn-MOF-derived carbon. When the additional amount (mass fraction) of flower-like Zn-MOF-derived carbon@MoS2 in paraffin was 25%, the frequency was 9.28 GHz, the matching thickness was 3 mm, and the effective absorption bandwidth was 3.04 GHz, the optimal reflection loss reached -49.68 dB, showing excellent electromagnetic wave absorption performance.
2023, 39(5): 841-852
doi: 10.11862/CJIC.2023.052
Abstract:
In this study, Cu/Fe bimetallic biochar composites (BC@Cu/Fe-X, X=3, 5, 10) and Fe biochar composites (BC@Fe) were prepared by one-step pyrolysis. The effect of Cu doping amount on the BC@Cu/Fe-X adsorption of Pb2+ was investigated and the optimum doping ratio was determined. The results showed that BC@Cu/Fe-5 had the best adsorption performance for Pb2+. The effects of adsorption time, Pb2+ concentration, pH, coexisting ions, aging in air, and other experimental conditions on the adsorption of Pb2+ by BC@Cu/Fe-5 were studied. The adsorption behavior of BC@Cu/Fe-5 on Pb2+ was analyzed by fitting the kinetic and thermodynamic data. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and other characterization techniques were used to analyze the changes of the characteristic peaks before and after the BC@Cu/Fe-5 adsorption of Pb2+. The adsorption mechanism of BC@Cu/Fe-5 on Pb2+ is that about 42% of Pb2+ is reduced to Pb0, 33% of Pb2+ forms PbO/Pb(OH)2, and 25% of Pb2+ forms complexes with functional groups such as O—H, C—O, C=O, COO, and Fe—O. Cu doping can improve the ability of Fe to reduce Pb2+.
In this study, Cu/Fe bimetallic biochar composites (BC@Cu/Fe-X, X=3, 5, 10) and Fe biochar composites (BC@Fe) were prepared by one-step pyrolysis. The effect of Cu doping amount on the BC@Cu/Fe-X adsorption of Pb2+ was investigated and the optimum doping ratio was determined. The results showed that BC@Cu/Fe-5 had the best adsorption performance for Pb2+. The effects of adsorption time, Pb2+ concentration, pH, coexisting ions, aging in air, and other experimental conditions on the adsorption of Pb2+ by BC@Cu/Fe-5 were studied. The adsorption behavior of BC@Cu/Fe-5 on Pb2+ was analyzed by fitting the kinetic and thermodynamic data. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and other characterization techniques were used to analyze the changes of the characteristic peaks before and after the BC@Cu/Fe-5 adsorption of Pb2+. The adsorption mechanism of BC@Cu/Fe-5 on Pb2+ is that about 42% of Pb2+ is reduced to Pb0, 33% of Pb2+ forms PbO/Pb(OH)2, and 25% of Pb2+ forms complexes with functional groups such as O—H, C—O, C=O, COO, and Fe—O. Cu doping can improve the ability of Fe to reduce Pb2+.
2023, 39(5): 853-858
doi: 10.11862/CJIC.2023.048
Abstract:
We have prepared well-defined supported nanocrystal catalysts using a thermal decomposition method.One dimensional ZnO nanorods were used as crystalline seeds during nanocrystal nucleation and growth.The growth of nanocrystals with different components on the surface of ZnO nanorods was systematically controlled.Moreover, well-defined MnO/ZnO, Co3O4/ZnO, and Co3Mn1/ZnO catalysts were synthesized by a modified thermal decomposition approach.Transmission electron microscope(TEM)and X ray powder diffraction(XRD)results showed that different nanocrystals were uniformly dispersed on the surface of assynthesized ZnO nanorods.The Co3Mn1/ZnO catalyst exhibited the best catalytic performance of CO oxidation compared to the MnO/ZnO and Co3O4/ZnO catalysts.The Co3Mn1/ZnO catalyst can easily catalyze CO oxidation at a lower temperature(50 ℃)with sustain- able durability.Moreover, the T100(the temperature when CO conversion reached 100%)of Co3Mn1/ZnO catalyst was 200 ℃ at gas hourly space velocity of 200 L·gcat-1·h-1.The surface characterization of the different catalysts was per- formed by using X-ray photoelectron spectroscopy(XPS).The results revealed that the Co3Mn1/ZnO catalyst had ap- proximately 30% more oxygen vacancy compared to the MnO/ZnO catalyst, resulting in a higher catalytic activity of the CO oxidation reaction.More importantly, the Co3Mn1/ZnO catalyst had a much lower apparent activation barrier(39.4 kJ·mol-1)than the other supported nanocrystal catalysts.
We have prepared well-defined supported nanocrystal catalysts using a thermal decomposition method.One dimensional ZnO nanorods were used as crystalline seeds during nanocrystal nucleation and growth.The growth of nanocrystals with different components on the surface of ZnO nanorods was systematically controlled.Moreover, well-defined MnO/ZnO, Co3O4/ZnO, and Co3Mn1/ZnO catalysts were synthesized by a modified thermal decomposition approach.Transmission electron microscope(TEM)and X ray powder diffraction(XRD)results showed that different nanocrystals were uniformly dispersed on the surface of assynthesized ZnO nanorods.The Co3Mn1/ZnO catalyst exhibited the best catalytic performance of CO oxidation compared to the MnO/ZnO and Co3O4/ZnO catalysts.The Co3Mn1/ZnO catalyst can easily catalyze CO oxidation at a lower temperature(50 ℃)with sustain- able durability.Moreover, the T100(the temperature when CO conversion reached 100%)of Co3Mn1/ZnO catalyst was 200 ℃ at gas hourly space velocity of 200 L·gcat-1·h-1.The surface characterization of the different catalysts was per- formed by using X-ray photoelectron spectroscopy(XPS).The results revealed that the Co3Mn1/ZnO catalyst had ap- proximately 30% more oxygen vacancy compared to the MnO/ZnO catalyst, resulting in a higher catalytic activity of the CO oxidation reaction.More importantly, the Co3Mn1/ZnO catalyst had a much lower apparent activation barrier(39.4 kJ·mol-1)than the other supported nanocrystal catalysts.
2023, 39(5): 859-866
doi: 10.11862/CJIC.2023.040
Abstract:
N-ethyl carbazol-3-formaldehyde was synthesized by using carbazole as initial material through a two-step reaction, and its crystal structure was determined by X-ray single crystal diffraction and showed that the crystal belongs to monoclinic, P21/n space group. A new fluorescent probe CMP for Cu2+ ions was designed and synthesized from N-ethyl carbazol-3-formaldehyde and 1,3-diamino-2-propanol. CMP in DMSO/H2O (6∶4, V/V, Tris-HCl buffer, pH=7.0) solution displayed highly selective and sensitive fluorescence "on-off" response over all the other competitive metal ions including K+, Ni2+, Pb2+, Sn2+, Mn2+, Fe3+, Fe2+, Cr3+, Co2+, Cd2+, Al3+, and Mg2+. The fluorescence intensity of CMP presented a good linear relationship to the Cu2+ concentration and with a low detection limit of 0.205 μmol·L-1 for Cu2+ ion, and the binding constant was calculated to be 1.52×105 L·mol-1. 1/(I0-I) of CMP vs cCu2+/cCMP plot, Job plot, and 1H NMR titration confirmed that fluorescence decrease was caused by the formation of 1∶2 complex between CMP and copper ion. The recovery tests demonstrated that CMP could accurately detect the existence of Cu2+ ions in water samples.
N-ethyl carbazol-3-formaldehyde was synthesized by using carbazole as initial material through a two-step reaction, and its crystal structure was determined by X-ray single crystal diffraction and showed that the crystal belongs to monoclinic, P21/n space group. A new fluorescent probe CMP for Cu2+ ions was designed and synthesized from N-ethyl carbazol-3-formaldehyde and 1,3-diamino-2-propanol. CMP in DMSO/H2O (6∶4, V/V, Tris-HCl buffer, pH=7.0) solution displayed highly selective and sensitive fluorescence "on-off" response over all the other competitive metal ions including K+, Ni2+, Pb2+, Sn2+, Mn2+, Fe3+, Fe2+, Cr3+, Co2+, Cd2+, Al3+, and Mg2+. The fluorescence intensity of CMP presented a good linear relationship to the Cu2+ concentration and with a low detection limit of 0.205 μmol·L-1 for Cu2+ ion, and the binding constant was calculated to be 1.52×105 L·mol-1. 1/(I0-I) of CMP vs cCu2+/cCMP plot, Job plot, and 1H NMR titration confirmed that fluorescence decrease was caused by the formation of 1∶2 complex between CMP and copper ion. The recovery tests demonstrated that CMP could accurately detect the existence of Cu2+ ions in water samples.
2023, 39(5): 867-873
doi: 10.11862/CJIC.2023.059
Abstract:
Complex 1 with 2-(4-methylphenyl)pyridine as C, N-ligand was used to react with NOBF4 under different conditions to afford two cyclometalated ruthenium(Ⅱ) nitrosyl complexes 2 and 3 in high yields. Herein, increasing temperature and aerobic conditions were favored by the generation of 3. NMR, MS, IR, and single-crystal X-ray structure analysis showed that these two nitrosyl complexes have {RuⅡ-NO+} characteristics. This was further confirmed by electrochemistry and UV-Vis absorption spectra. Subsequently, the photolyzed product of ruthenium nitrosyl complex 2 was separated and characterized by NMR and MS spectra. The result showed that such nitrosyl complexes could give a release of NO by the breakage of Ru—NO under the light, along with Ru(Ⅱ) as the oxidation state.
Complex 1 with 2-(4-methylphenyl)pyridine as C, N-ligand was used to react with NOBF4 under different conditions to afford two cyclometalated ruthenium(Ⅱ) nitrosyl complexes 2 and 3 in high yields. Herein, increasing temperature and aerobic conditions were favored by the generation of 3. NMR, MS, IR, and single-crystal X-ray structure analysis showed that these two nitrosyl complexes have {RuⅡ-NO+} characteristics. This was further confirmed by electrochemistry and UV-Vis absorption spectra. Subsequently, the photolyzed product of ruthenium nitrosyl complex 2 was separated and characterized by NMR and MS spectra. The result showed that such nitrosyl complexes could give a release of NO by the breakage of Ru—NO under the light, along with Ru(Ⅱ) as the oxidation state.
2023, 39(5): 874-882
doi: 10.11862/CJIC.2023.050
Abstract:
Three organotin 2, 2′-biphenyl dicarboxylates, namely [((PhC(Me)2CH2)3Sn)2(DPA)] (1), [(Cy)3Sn(DPA)]n (2), and [(n-Bu)2Sn(DPA)]n (3), have been prepared by the microwave-assisted solvothermal reaction of 2, 2′-biphenyl dicarboxylic acid (H2DPA) with bis(tri(2-methyl-2-phenyl)propyl)tin oxide, tricyclohexyltin hydroxide, and dibutyltin oxide, respectively. Complexes 1-3 have been characterized by IR, NMR, elemental analysis, and thermogravimetry, and the crystal structures have been determined by X-ray diffraction. The crystals of 1-3 belong to the monoclinic system. Due to the influence of alkyl group steric, the steric resistance of the group for PhC(Me)2CH2 (1) > Cy (2) > n-Bu (3), the coordination number of tin atoms of complexes 1-3 increases successively, and the coordination number of tin atoms are 4, 5, and 6, respectively. Complex 1 has a binuclear structure, and complexes 2 and 3 are 1D chain structures. The antitumor activity shows that complexes 1-3 have higher activities than cisplatin in Human lung cancer cells (NCI-H460), human breast adenocarcinoma cells (MCF-7), and human liver cancer cells (HepG2) line in vitro.
Three organotin 2, 2′-biphenyl dicarboxylates, namely [((PhC(Me)2CH2)3Sn)2(DPA)] (1), [(Cy)3Sn(DPA)]n (2), and [(n-Bu)2Sn(DPA)]n (3), have been prepared by the microwave-assisted solvothermal reaction of 2, 2′-biphenyl dicarboxylic acid (H2DPA) with bis(tri(2-methyl-2-phenyl)propyl)tin oxide, tricyclohexyltin hydroxide, and dibutyltin oxide, respectively. Complexes 1-3 have been characterized by IR, NMR, elemental analysis, and thermogravimetry, and the crystal structures have been determined by X-ray diffraction. The crystals of 1-3 belong to the monoclinic system. Due to the influence of alkyl group steric, the steric resistance of the group for PhC(Me)2CH2 (1) > Cy (2) > n-Bu (3), the coordination number of tin atoms of complexes 1-3 increases successively, and the coordination number of tin atoms are 4, 5, and 6, respectively. Complex 1 has a binuclear structure, and complexes 2 and 3 are 1D chain structures. The antitumor activity shows that complexes 1-3 have higher activities than cisplatin in Human lung cancer cells (NCI-H460), human breast adenocarcinoma cells (MCF-7), and human liver cancer cells (HepG2) line in vitro.
2023, 39(5): 883-890
doi: 10.11862/CJIC.2023.057
Abstract:
Different composite photoanodes with double-layer structure applied to dye-sensitized solar cell (DSSC) can be prepared by core - shell structure Au@SiO2@CeO2 nanospheres synthesized by hydrothermal method. The results showed that the photoelectric conversion efficiency of the solar cells could be significantly improved when CeO2 nanospheres and Au@SiO2@CeO2 nanospheres coating were applied to the photoanode scattering layer of DSSC. Compared with the pure TiO2 (P25) photoanode, the photoelectric property of P25/CeO2 nanosphere photoanode cells increased by 15.3%, and that of P25/Au@SiO2@CeO2 nanosphere photoanode cells increased by 27.9%. Why the photoelectric property of DSSC can be enhanced is mainly attributed to the following two dimensions. On the one hand, the light scattering effect of the photoanode film is effectively heightened by the localized plasmon resonance of the Au nanoparticles. On the other hand, the light scattering effect and the electron transmission capacity are enhanced since the CeO2 has the high load capacity in the dye, the core-shell structure with a high specific surface area.
Different composite photoanodes with double-layer structure applied to dye-sensitized solar cell (DSSC) can be prepared by core - shell structure Au@SiO2@CeO2 nanospheres synthesized by hydrothermal method. The results showed that the photoelectric conversion efficiency of the solar cells could be significantly improved when CeO2 nanospheres and Au@SiO2@CeO2 nanospheres coating were applied to the photoanode scattering layer of DSSC. Compared with the pure TiO2 (P25) photoanode, the photoelectric property of P25/CeO2 nanosphere photoanode cells increased by 15.3%, and that of P25/Au@SiO2@CeO2 nanosphere photoanode cells increased by 27.9%. Why the photoelectric property of DSSC can be enhanced is mainly attributed to the following two dimensions. On the one hand, the light scattering effect of the photoanode film is effectively heightened by the localized plasmon resonance of the Au nanoparticles. On the other hand, the light scattering effect and the electron transmission capacity are enhanced since the CeO2 has the high load capacity in the dye, the core-shell structure with a high specific surface area.
2023, 39(5): 891-905
doi: 10.11862/CJIC.2023.049
Abstract:
The sole micropores strictly restrict the wide utilization of TS-1 zeolite in the catalytic fields, especially in the catalytic conversion of compounds with large molecular sizes. Here, we report a feasible and economical method to overcome this drawback. In this work, the hierarchical TS-1 zeolite was constructed via post-acid treatment, postalkali etching, and a combination of postacid treatment and alkali etching methods, after which, the corresponding NiMo-supported catalysts were prepared via the incipient wetness impregnation method. Then, the aforementioned materials were fully characterized using X - ray diffraction (XRD), N2 adsorption - desorption, pyridine adsorbed Fourier transform infrared spectroscopy (Py - FTIR), H2 temperature programmed reduction (H2 - TPR), X-ray photoelectron spectroscopy (XPS), and high-resolution transition electron microscope (HR-TEM) to unravel the changes in the physicochemical properties caused by the post treatments. Finally, the hydrodesulfurization of dibenzothiophene (DBT) was used as a probe to assess the effects of the post-treatments on the catalytic performance of the hierarchical NiMo/TS-1 catalysts. The results showed that the MFI topology of TS-1 zeolite remained undamaged significantly and the serial hierarchical TS-1 zeolites exhibited higher specific surface areas and mesopore structures. Moreover, appropriate amounts of Br?nsted acid sites were formed at the surface of the serial hierarchical TS-1 zeolites. The interaction between the active metals and the support materials was also modulated by the posttreatment of TS-1 zeolite, which resulted in better dispersion of Ni promoted MoS2 slabs with a higher proportion of NiMoS active phase, further leading to the enhanced catalytic activity and direct desulfurization pathway selectivity of the corresponding serial hierarchical NiMo/TS-1 catalysts. Among all the prepared catalysts, the catalytic activity was enhanced by approximately 1.2 times over catalyst NiMo/AT-TS-1 obtained by post-acid treatment compared to that over catalyst NiMo/TS-1 without treatment and on which the selectivity of the DDS pathway was 22% higher compared to that over catalyst NiMo/TS-1.
The sole micropores strictly restrict the wide utilization of TS-1 zeolite in the catalytic fields, especially in the catalytic conversion of compounds with large molecular sizes. Here, we report a feasible and economical method to overcome this drawback. In this work, the hierarchical TS-1 zeolite was constructed via post-acid treatment, postalkali etching, and a combination of postacid treatment and alkali etching methods, after which, the corresponding NiMo-supported catalysts were prepared via the incipient wetness impregnation method. Then, the aforementioned materials were fully characterized using X - ray diffraction (XRD), N2 adsorption - desorption, pyridine adsorbed Fourier transform infrared spectroscopy (Py - FTIR), H2 temperature programmed reduction (H2 - TPR), X-ray photoelectron spectroscopy (XPS), and high-resolution transition electron microscope (HR-TEM) to unravel the changes in the physicochemical properties caused by the post treatments. Finally, the hydrodesulfurization of dibenzothiophene (DBT) was used as a probe to assess the effects of the post-treatments on the catalytic performance of the hierarchical NiMo/TS-1 catalysts. The results showed that the MFI topology of TS-1 zeolite remained undamaged significantly and the serial hierarchical TS-1 zeolites exhibited higher specific surface areas and mesopore structures. Moreover, appropriate amounts of Br?nsted acid sites were formed at the surface of the serial hierarchical TS-1 zeolites. The interaction between the active metals and the support materials was also modulated by the posttreatment of TS-1 zeolite, which resulted in better dispersion of Ni promoted MoS2 slabs with a higher proportion of NiMoS active phase, further leading to the enhanced catalytic activity and direct desulfurization pathway selectivity of the corresponding serial hierarchical NiMo/TS-1 catalysts. Among all the prepared catalysts, the catalytic activity was enhanced by approximately 1.2 times over catalyst NiMo/AT-TS-1 obtained by post-acid treatment compared to that over catalyst NiMo/TS-1 without treatment and on which the selectivity of the DDS pathway was 22% higher compared to that over catalyst NiMo/TS-1.
2023, 39(5): 906-916
doi: 10.11862/CJIC.2023.063
Abstract:
A millimeter-sized macro-mesoporous SiO2 (MMS) was prepared by a dual-templating method, using an epoxy resin macroporous polymer with 3D skeleton structure as the macroscopic shape and macropore structure directing agent and PEG 2000 as the mesopore porogen and the PDA-modified MMS (PDA/MMS, PDA=polydopamine) was obtained via the oxidative self-polymerization of dopamine (DA) on the pore wall of MMS, then the in situ reduction of Ag+ by the PDA on the surface of PDA/MMS formed the macro-mesoporous Ag/PDA/MMS composite. The as-prepared materials were characterized by scanning electron microscope, transmission electron microscope, N2 adsorption-desorption, X-ray photoelectron spectroscopy, X-ray diffraction, UV-Vis, FT-IR, and thermogravimetry techniques. The results show that MMS has the advantages of both nano-mesoporous materials and macro-sized macroporous materials, and possesses large specific surface area and pore volume, and high mechanical strength. Ag/PDA/MMS exhibited high catalytic activity in the reduction of p-nitrophenol (4-NP), and the turnover frequency (TOF) reached 2.97 min-1, which is attributed to its unique structure: the interconnected macropores greatly reduce mass transfer resistance, the short mesopore channels significantly increase the accessibility of active sites and effectively confine the size of silver nanoparticles, and the large specific surface area provides a large number of active sites for reactants. Moreover, the millimeter-sized Ag/PDA/MMS could be easily separated from the reaction system, and it could still convert 4-NP to p-aminophenol (4-AP) completely after five cycles. In addition, Ag/PDA/ MMS also showed a good catalytic effect in the reduction of methylene blue (MB).
A millimeter-sized macro-mesoporous SiO2 (MMS) was prepared by a dual-templating method, using an epoxy resin macroporous polymer with 3D skeleton structure as the macroscopic shape and macropore structure directing agent and PEG 2000 as the mesopore porogen and the PDA-modified MMS (PDA/MMS, PDA=polydopamine) was obtained via the oxidative self-polymerization of dopamine (DA) on the pore wall of MMS, then the in situ reduction of Ag+ by the PDA on the surface of PDA/MMS formed the macro-mesoporous Ag/PDA/MMS composite. The as-prepared materials were characterized by scanning electron microscope, transmission electron microscope, N2 adsorption-desorption, X-ray photoelectron spectroscopy, X-ray diffraction, UV-Vis, FT-IR, and thermogravimetry techniques. The results show that MMS has the advantages of both nano-mesoporous materials and macro-sized macroporous materials, and possesses large specific surface area and pore volume, and high mechanical strength. Ag/PDA/MMS exhibited high catalytic activity in the reduction of p-nitrophenol (4-NP), and the turnover frequency (TOF) reached 2.97 min-1, which is attributed to its unique structure: the interconnected macropores greatly reduce mass transfer resistance, the short mesopore channels significantly increase the accessibility of active sites and effectively confine the size of silver nanoparticles, and the large specific surface area provides a large number of active sites for reactants. Moreover, the millimeter-sized Ag/PDA/MMS could be easily separated from the reaction system, and it could still convert 4-NP to p-aminophenol (4-AP) completely after five cycles. In addition, Ag/PDA/ MMS also showed a good catalytic effect in the reduction of methylene blue (MB).
2023, 39(5): 917-927
doi: 10.11862/CJIC.2023.053
Abstract:
A novel Ho4 complex, namely [Ho4(NO3)2(acac)4(L)2(CH3OH)2]·2CH3CN, where H4L=(E)-2-(hydroxymethyl)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)propane-1,3-diol and acac=acetylacetone, has been constructed by using a polydentate Schiff base ligand (H4L) reacting with Ho(acac)3·2H2O. X-ray diffraction analysis indicates that complex 1 shows a central symmetric tetranuclear structure. Both eight-coordinated Ho1(Ⅲ) and Ho2(Ⅲ) ions possess a distorted triangular dodecahedron geometrical configuration. Complex 1 shows good solvent stability. The magnetic study reveals that complex 1 exhibits a slow relaxation of the magnetization behavior. To our knowledge, complex 1 is a rarely Ho(Ⅲ)-based complex displaying slow magnetic relaxation behavior under Hdc=0 Oe filed. Interestingly, complex 1 exhibited high catalytic activity and could effectively catalyze the cycloaddition reaction of CO2 with vari-ous epoxides.
A novel Ho4 complex, namely [Ho4(NO3)2(acac)4(L)2(CH3OH)2]·2CH3CN, where H4L=(E)-2-(hydroxymethyl)-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)propane-1,3-diol and acac=acetylacetone, has been constructed by using a polydentate Schiff base ligand (H4L) reacting with Ho(acac)3·2H2O. X-ray diffraction analysis indicates that complex 1 shows a central symmetric tetranuclear structure. Both eight-coordinated Ho1(Ⅲ) and Ho2(Ⅲ) ions possess a distorted triangular dodecahedron geometrical configuration. Complex 1 shows good solvent stability. The magnetic study reveals that complex 1 exhibits a slow relaxation of the magnetization behavior. To our knowledge, complex 1 is a rarely Ho(Ⅲ)-based complex displaying slow magnetic relaxation behavior under Hdc=0 Oe filed. Interestingly, complex 1 exhibited high catalytic activity and could effectively catalyze the cycloaddition reaction of CO2 with vari-ous epoxides.
2023, 39(5): 928-938
doi: 10.11862/CJIC.2023.047
Abstract:
A series of complexes constructed by 2,2′∶6,2″-terpyridine-4-carboxylic acid (Htpc), namely [Cr2(tpc)2 (HCOO)2(OH)2]·4H2O (1), [Ba(tpc)2(H2O)2]n (2), [Zn2(tpc)2(NO3)2]n (3), [Pb(Htpc)(NO3)2]·2H2O (4), and [Rh(Htpc)Cl3]·CH3OH·H2O (5), have been prepared under solvothermal conditions. Single crystal X-ray analysis reveals that the organic ligands took four different coordination fashions in 1-5. Complexes 1-5 show novel supramolecular networks through rich C—H…O/N hydrogen bonds and π…π contacts. The luminescence of the complexes was investigated and under 365 nm ultraviolet radiation the crystals of 2-5 displayed green, blue, purple-blue, and golden colors, respectively.
A series of complexes constructed by 2,2′∶6,2″-terpyridine-4-carboxylic acid (Htpc), namely [Cr2(tpc)2 (HCOO)2(OH)2]·4H2O (1), [Ba(tpc)2(H2O)2]n (2), [Zn2(tpc)2(NO3)2]n (3), [Pb(Htpc)(NO3)2]·2H2O (4), and [Rh(Htpc)Cl3]·CH3OH·H2O (5), have been prepared under solvothermal conditions. Single crystal X-ray analysis reveals that the organic ligands took four different coordination fashions in 1-5. Complexes 1-5 show novel supramolecular networks through rich C—H…O/N hydrogen bonds and π…π contacts. The luminescence of the complexes was investigated and under 365 nm ultraviolet radiation the crystals of 2-5 displayed green, blue, purple-blue, and golden colors, respectively.
2023, 39(5): 939-946
doi: 10.11862/CJIC.2023.056
Abstract:
One metal-organic framework [Cd3(L)2(H2O)9]·9H2O (MOF 1), where H3L=5-(((4-carboxyphenyl)oxy)methyl) benzene-1,3-dicarboxylic acid, has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and elemental analysis. MOF 1 exhibits a 2D microporous structure with an accessible volume of 22.4%. Luminescent property studies reveal that MOF 1 can act as a promising luminescent sensor for detecting Fe(Ⅲ) and Cr(Ⅵ) with high selectivities and low detection limits, which are additionally free from the interference of other ions. Moreover, the mechanism of selective quenching was studied by measuring the UV-Vis absorption of the host metal-organic framework and the target analyte ions. The fluorescence resonance energy transfer is the possible mechanism involved in the quenching of the fluorescence intensity.
One metal-organic framework [Cd3(L)2(H2O)9]·9H2O (MOF 1), where H3L=5-(((4-carboxyphenyl)oxy)methyl) benzene-1,3-dicarboxylic acid, has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and elemental analysis. MOF 1 exhibits a 2D microporous structure with an accessible volume of 22.4%. Luminescent property studies reveal that MOF 1 can act as a promising luminescent sensor for detecting Fe(Ⅲ) and Cr(Ⅵ) with high selectivities and low detection limits, which are additionally free from the interference of other ions. Moreover, the mechanism of selective quenching was studied by measuring the UV-Vis absorption of the host metal-organic framework and the target analyte ions. The fluorescence resonance energy transfer is the possible mechanism involved in the quenching of the fluorescence intensity.
2023, 39(5): 947-958
doi: 10.11862/CJIC.2023.065
Abstract:
A new cyano-equipped dithienylethene in closed-ring form (Lc) was first isolated and structurally characterized by IR, 1H NMR, and X-ray single-crystal diffraction. It showed an interesting racemic mixture of R,R and S,S enantiomer pairs evidencing the structural transformation from 1,3,5-hexatriene to cyclohexadiene in the photochemical conrotatory cyclization. Followed UV-Vis spectral investigations exhibited its reversible photochromism in both THF solution and solid state with the maximum absorption wavelength of 607 nm observed in the visible band. The photo-isomerization kinetics of the compound indicated a first-order process for photo-reversion and zeroth-order for photo-cyclization. The compound was further used as a ligand to self-assemble with Ag(CF3SO3) resulting in complex 1. Its structure was characterized by elemental analysis, IR, 1H NMR, and ESI-MS. Complex 1 demonstrated reversible photochromism in the solid state with the same λmax as the closed-ring ligand. Unlike the complex derived from the open-ring ligand, Ag(Ⅰ) ions coordination with the closed-ring ligand doesn′t modify the absorption due to the restricted free rotation of the thienyl rings in the rigid configuration of the closed-ring ligand. In comparison with the open-ring ligand, 1 displayed a faster photo-isomerization rate corresponding to the smaller band gap determined by cyclic voltammetry.
A new cyano-equipped dithienylethene in closed-ring form (Lc) was first isolated and structurally characterized by IR, 1H NMR, and X-ray single-crystal diffraction. It showed an interesting racemic mixture of R,R and S,S enantiomer pairs evidencing the structural transformation from 1,3,5-hexatriene to cyclohexadiene in the photochemical conrotatory cyclization. Followed UV-Vis spectral investigations exhibited its reversible photochromism in both THF solution and solid state with the maximum absorption wavelength of 607 nm observed in the visible band. The photo-isomerization kinetics of the compound indicated a first-order process for photo-reversion and zeroth-order for photo-cyclization. The compound was further used as a ligand to self-assemble with Ag(CF3SO3) resulting in complex 1. Its structure was characterized by elemental analysis, IR, 1H NMR, and ESI-MS. Complex 1 demonstrated reversible photochromism in the solid state with the same λmax as the closed-ring ligand. Unlike the complex derived from the open-ring ligand, Ag(Ⅰ) ions coordination with the closed-ring ligand doesn′t modify the absorption due to the restricted free rotation of the thienyl rings in the rigid configuration of the closed-ring ligand. In comparison with the open-ring ligand, 1 displayed a faster photo-isomerization rate corresponding to the smaller band gap determined by cyclic voltammetry.
2023, 39(5): 959-966
doi: 10.11862/CJIC.2023.064
Abstract:
Two anthracene-based complexes [Au(anbdtim)2]PF6 (1) and [Au(anbdtim)2][Au(CN)2] (2) have been synthesized, where anbdtim=2-(anthracenyl)-4, 5-bis(2, 5-dimethyl(3-thienyl))-1-methyl-imidazole. The different counter anions, PF6- in 1 and [Au(CN)2]- in 2, led to significantly different fluorescence between 1 and 2 both in solution and in the solid state. Complexes 1 and 2 in CH2Cl2 revealed an emission at 465 and 445 nm, respectively, and their solidstate luminescence exhibited an emission at 450 nm for 1 and 478 nm for 2. Interestingly, the luminescence of 2 was sensitive to benzene molecules, with an emission at 475 nm (quantum yield Φ=66.5%) in benzene while 448 nm (Φ=22.9%) in CH2Cl2. Moreover, the blue-green-emitting solid 2-benzene was prepared by the evaporation of a benzene solution of complex 2. This solid exhibited reversible luminescence switching between blue-green emission at 491 nm and steel-blue emission at 460 nm upon alternately removing and incorporating benzene molecules. On the basis of these experimental results, we discussed the influence of counter anions and benzene molecules on the luminescence behaviours of 1 and 2.
Two anthracene-based complexes [Au(anbdtim)2]PF6 (1) and [Au(anbdtim)2][Au(CN)2] (2) have been synthesized, where anbdtim=2-(anthracenyl)-4, 5-bis(2, 5-dimethyl(3-thienyl))-1-methyl-imidazole. The different counter anions, PF6- in 1 and [Au(CN)2]- in 2, led to significantly different fluorescence between 1 and 2 both in solution and in the solid state. Complexes 1 and 2 in CH2Cl2 revealed an emission at 465 and 445 nm, respectively, and their solidstate luminescence exhibited an emission at 450 nm for 1 and 478 nm for 2. Interestingly, the luminescence of 2 was sensitive to benzene molecules, with an emission at 475 nm (quantum yield Φ=66.5%) in benzene while 448 nm (Φ=22.9%) in CH2Cl2. Moreover, the blue-green-emitting solid 2-benzene was prepared by the evaporation of a benzene solution of complex 2. This solid exhibited reversible luminescence switching between blue-green emission at 491 nm and steel-blue emission at 460 nm upon alternately removing and incorporating benzene molecules. On the basis of these experimental results, we discussed the influence of counter anions and benzene molecules on the luminescence behaviours of 1 and 2.
2023, 39(5): 967-978
doi: 10.11862/CJIC.2023.055
Abstract:
A series of xMoO3/NiO-Al2O3 catalysts (x% represented the mass fraction of MoO3) were prepared by double hydrolytic co-precipitation method combined with impregnation method. The methanation reaction activity and sulfur resistance of catalysts were evaluated using a fixed-bed reactor, and the catalysts were characterized in detail fresh and after deactivation. The results showed that the low-temperature methanation activity of the catalyst decreased with the increase in MoO3 loading, whereas the sulfur resistance of the catalyst was significantly enhanced after MoO3 doping. The decrease in catalyst activity for low-temperature methanation was attributed to the fact that the increase in MoO3 loading reduced the active specific surface area of the catalyst, but the introduction of MoO3 also provided a competitive adsorption site for sulfide, which can delay sulfur poisoning at the active site. The xMoO3/NiO-Al2O3 catalyst with 12.5% MoO3 loading (mass fraction) maintained the highest methanation activity for 7 h in the presence of 143 mg·m-3 H2S/H2 (81.1% CO conversion, 550 ℃). The sulfur chemisorption content of 12.5MoO3/NiO-Al2O3 catalyst reaching 0.71% (mass fraction) was 1.48 times that of NiO-Al2O3 catalyst and further XPS also confirmed that the amount of MoS2 generated was the highest, which indicated that Mo preferentially adsorbs more sulfur and protects the active site. In addition, at a MoO3 loading of 12.5%, MoO3 on the surface of the catalyst reached the threshold of monolayer dispersion, which can provide more adsorption sites for sulfides when competitive adsorption occurs.
A series of xMoO3/NiO-Al2O3 catalysts (x% represented the mass fraction of MoO3) were prepared by double hydrolytic co-precipitation method combined with impregnation method. The methanation reaction activity and sulfur resistance of catalysts were evaluated using a fixed-bed reactor, and the catalysts were characterized in detail fresh and after deactivation. The results showed that the low-temperature methanation activity of the catalyst decreased with the increase in MoO3 loading, whereas the sulfur resistance of the catalyst was significantly enhanced after MoO3 doping. The decrease in catalyst activity for low-temperature methanation was attributed to the fact that the increase in MoO3 loading reduced the active specific surface area of the catalyst, but the introduction of MoO3 also provided a competitive adsorption site for sulfide, which can delay sulfur poisoning at the active site. The xMoO3/NiO-Al2O3 catalyst with 12.5% MoO3 loading (mass fraction) maintained the highest methanation activity for 7 h in the presence of 143 mg·m-3 H2S/H2 (81.1% CO conversion, 550 ℃). The sulfur chemisorption content of 12.5MoO3/NiO-Al2O3 catalyst reaching 0.71% (mass fraction) was 1.48 times that of NiO-Al2O3 catalyst and further XPS also confirmed that the amount of MoS2 generated was the highest, which indicated that Mo preferentially adsorbs more sulfur and protects the active site. In addition, at a MoO3 loading of 12.5%, MoO3 on the surface of the catalyst reached the threshold of monolayer dispersion, which can provide more adsorption sites for sulfides when competitive adsorption occurs.
2023, 39(5): 979-991
doi: 10.11862/CJIC.2023.054
Abstract:
Core-shell structure precursor Ni0.80Co0.15Al0.05(OH)2 was synthesized via co-precipitation by adjusting the Al solution with three flow rates (Each flow rate worked for three hours). The core of the precursor was a uniform structure with a composition of Ni0.88Co0.12(OH)2; and the shell of the precursor was a concentration-gradient structure with a composition of Ni0.72Co0.18Al0.10(OH)2, which Ni content decreased gradually while Al content increased steadily from the surface of the core to the particle surface. A mixture of this core-shell structure precursor and LiOH·H2O was sintered at 700 ℃ for different sintering times in the O2 atmosphere to obtain a full concentration gradient and spherical LiNi0.80Co0.15Al0.05O2. The diffusion of Ni, Co, and Al under different calcination times led to a concentration gradient variation of LiNi0.80Co0.15Al0.05O2, which displayed different electrochemical performance. When the sintering time was 12 h, the obtained material had a well-designed concentration-gradient structure: from the core to particle surface, the content (atomic fraction) of Ni decreased from 0.855 to 0.732, while the content of Al content increased steadily from 0.003 to 0.115. And the content of Co first increased from 0.142 to 0.163 and then decreased to 0.153. This cathode material had a lower degree of cation mixing and well-developed layered characteristics. It had a discharge capacity of 201.3 mAh·g-1 at 0.2C, which was just under 205.8 mAh·g-1 of the homogeneous one; and it showed excellent capacity retention of 71.6% after 200 cycles, which was much higher than that of the homogeneous material (54.6%). It is attributed to a good Ni-deficient and Al/Co-rich out-layer, which can reduce anisotropic volume variations and electrode polarization during cycling. As a result, it could reduce the charge-transfer resistance of the electrode, and prevent the formation and extension of micro-cracks on the electrode′s surface. This cathode material is easy for industrial application because the pH value of the co-precipitation reaction is quite stable and its concentration gradient structure is controllable by adjusting the flow rates of the Al solution and the calcination time. Furthermore, the pH value of the co-precipitation reaction shifted only when the injection rate of the Al solution was adjusted. After that, the pH value quickly returned to keep constant, and the precursor had high crystallinity and good consistency of the material.
Core-shell structure precursor Ni0.80Co0.15Al0.05(OH)2 was synthesized via co-precipitation by adjusting the Al solution with three flow rates (Each flow rate worked for three hours). The core of the precursor was a uniform structure with a composition of Ni0.88Co0.12(OH)2; and the shell of the precursor was a concentration-gradient structure with a composition of Ni0.72Co0.18Al0.10(OH)2, which Ni content decreased gradually while Al content increased steadily from the surface of the core to the particle surface. A mixture of this core-shell structure precursor and LiOH·H2O was sintered at 700 ℃ for different sintering times in the O2 atmosphere to obtain a full concentration gradient and spherical LiNi0.80Co0.15Al0.05O2. The diffusion of Ni, Co, and Al under different calcination times led to a concentration gradient variation of LiNi0.80Co0.15Al0.05O2, which displayed different electrochemical performance. When the sintering time was 12 h, the obtained material had a well-designed concentration-gradient structure: from the core to particle surface, the content (atomic fraction) of Ni decreased from 0.855 to 0.732, while the content of Al content increased steadily from 0.003 to 0.115. And the content of Co first increased from 0.142 to 0.163 and then decreased to 0.153. This cathode material had a lower degree of cation mixing and well-developed layered characteristics. It had a discharge capacity of 201.3 mAh·g-1 at 0.2C, which was just under 205.8 mAh·g-1 of the homogeneous one; and it showed excellent capacity retention of 71.6% after 200 cycles, which was much higher than that of the homogeneous material (54.6%). It is attributed to a good Ni-deficient and Al/Co-rich out-layer, which can reduce anisotropic volume variations and electrode polarization during cycling. As a result, it could reduce the charge-transfer resistance of the electrode, and prevent the formation and extension of micro-cracks on the electrode′s surface. This cathode material is easy for industrial application because the pH value of the co-precipitation reaction is quite stable and its concentration gradient structure is controllable by adjusting the flow rates of the Al solution and the calcination time. Furthermore, the pH value of the co-precipitation reaction shifted only when the injection rate of the Al solution was adjusted. After that, the pH value quickly returned to keep constant, and the precursor had high crystallinity and good consistency of the material.
