K2Ti6O13 whiskers were synthesized by conventional sol-gel method, sono-chemical assisted and microwave assisted sol-gel method in order to obtain catalysts with different particle sizes and to modify their optical, t...K2Ti6O13 whiskers were synthesized by conventional sol-gel method, sono-chemical assisted and microwave assisted sol-gel method in order to obtain catalysts with different particle sizes and to modify their optical, textural and electrochemical properties. These modifications improved their photocatalytic activity for H2 evolution and CO2 photo-reduction. Long K2Ti6O13 whiskers prepared by ultrasound assisted sol-gel method are the most active photocatalysts for the hydrogen evolution reaction using pure water as reactant (U-SG, 10,065 μmol g^-1). In contrast, an opposite behavior was observed using a mixture of ethanol-water, where the highest activity was achieved by the shortest and less crystalline K2Ti6O13 whiskers (C-SG, 3,2871 μmol g^-1). In case of CO2 photo-reduction, long whiskers that were also prepared by the sono-chemical assisted sol-gel method were the most active to transform CO2 to formaldehyde, methane, methanol and hydrogen. The EFB value of this catalyst is located very close to the potential for formaldehyde production and favors the selectivity to this organic product.展开更多
A spinel oxide NiCo204 prepared by thermal decomposition is of very high activity for the oxygen evolution reaction(OER)in alkaline solution.The oxygen evolution overpotential on NiCo204 is 0.252-0.262V in 10 M NaOH s...A spinel oxide NiCo204 prepared by thermal decomposition is of very high activity for the oxygen evolution reaction(OER)in alkaline solution.The oxygen evolution overpotential on NiCo204 is 0.252-0.262V in 10 M NaOH solution at 343K and current density 100 mAcm^(-2).展开更多
Implementation of non-precious electrocatalysts is key-enabling for water electrolysis to relieve challenges in energy and environmental sustainability. Self-supporting Ni-V2O3 electrodes consisting of nanostrip-like ...Implementation of non-precious electrocatalysts is key-enabling for water electrolysis to relieve challenges in energy and environmental sustainability. Self-supporting Ni-V2O3 electrodes consisting of nanostrip-like V2O3 perpendicularly anchored on Ni meshes are herein constructed via the electrochemical reduction of soluble NaVO3 in molten salts for enhanced electrocatalytic hydrogen evolution. Such a special configuration in morphology and composition creates a well confined interface between Ni and V2O3. Experimental and Density-Functional-Theory results confirm that the synergy between Ni and V2O3 accelerates the dissociation of H2O for forming hydrogen intermediates and enhances the combination of H*for generating H2.展开更多
Development of high efficient and stable water oxidation catalysts is essential for the realization of industrial water-splitting systems. Herein, a novel approach involving an in-situ transformation of Co(OH)2 nanosh...Development of high efficient and stable water oxidation catalysts is essential for the realization of industrial water-splitting systems. Herein, a novel approach involving an in-situ transformation of Co(OH)2 nanosheets into NH4 CoPO4·H2 O nanoplates on Co foil is reported. As a 3 D self-supported oxygen revolution reaction(OER) electrocatalyst, the as-prepared NH4 CoPO4·H2 O/Co exhibits remarkable catalytic activity and exceptional stability. Specifically, it can deliver a current density of 10 m A cm^(-2) at a quite low overpotential of 254 m V with a small Tafel slope of 64.4 m V dec-1 in alkaline electrolyte. Through experimental study and theoretical analysis, the excellent OER performance can be attributed to enriched exposed active sites, favorable electron/proton transfer and mass transport, and its unique asymmetric local atomic and electronic structure. Thus, this present research not only provides a practicable in-situ transformation strategy to design 3 D self-supported electrocatalysts, but also enlightens a new way of developing transition-metal phosphates for efficient and stable water oxidation at atomic level.展开更多
Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesd...Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr3Fe2O7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge disproportionation of Fe4+, the OER activity of Sr3Fe2O7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe4+. When metal substitution was made to Sr3Fe2O7 for stabilizing Fe4+ at room temperature, the temperature dependence of the OER activity disappeared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe4+ is substantially important for achieving high OER activity.展开更多
To accelerate the kinetics of oxygen evolution reaction(OER)regarding the energy conversion and storage approaches,the discovery of desirable cost-effective and highly efficient electrocatalysts is of prime importance...To accelerate the kinetics of oxygen evolution reaction(OER)regarding the energy conversion and storage approaches,the discovery of desirable cost-effective and highly efficient electrocatalysts is of prime importance.This study demonstrates a layered CaCo_2O_4with a two-dimensional nanoplate structure,which possesses electrocatalytic activity for OER.The OER activity was achieved on CaCo_2O_4with a Tafel slope of 71 mV dec^(-1)and a current density of 10 mA cm^(-2)at an overpotential of 371 mV,which was more active than the similar structure LiCoO_2catalyst.Combined with X-ray absorption fine structure and density functional theory calculations,the enhanced OER activity and stability are mainly attributed to the unique electronic structure derived from the interaction of Ca and Co,and improved electrical conductivity.CaCo_2O_4can be developed as a highly active and earth-abundant catalyst for OER in energy conversion and storage technologies.展开更多
Physiological changes in the photosynthesis, respiration and cell division of Chlamydomonas reinhardtii, a freshwater green alga, in response to adenine nucleotides were investigated. In advance of this investigation,...Physiological changes in the photosynthesis, respiration and cell division of Chlamydomonas reinhardtii, a freshwater green alga, in response to adenine nucleotides were investigated. In advance of this investigation, two adenine nucleotides, di(2'-O-methyl)-cyclic bis(3'-5')diadenylic acid (1) and its N-benzoyl-protected analog 2 were synthesized from the commercially available adenosine phosphoramidite. The respective analogs significantly promoted the cell division (cell number) of C. reinhardtii strains 137c mt+ and BR mt+. Moreover, they significantly enhanced the O2 evolution (photosynthesis) and O2 uptake (respiration) of both strains. c-di-AMP analogs seem to play an effective role as a physiological activator in planta.展开更多
In the semiconductor-based photocatalysts for overall water splitting, loading proper cocatalysts play a crucial role in enhancing the photocatalytic activity. In this work, we have chosen Ni_n/α-Ga_2O_3 as a model a...In the semiconductor-based photocatalysts for overall water splitting, loading proper cocatalysts play a crucial role in enhancing the photocatalytic activity. In this work, we have chosen Ni_n/α-Ga_2O_3 as a model and provided detailed density functional theory calculations to investigate the function of cocatalysts in hydrogen evolution reaction(HER). We have studied the formation and stability of Ni_n(n = 1–4) cluster on two stable surfaces of α-Ga_2O_3(001) and(012). In a Ni_n/α-Ga_2O_3 system, as the Ni 3d states well overlap with O and Ga states, the excited electrons transferred from Ga to Ni may participate in HER. We theoretically predict that introduction of Nincluster on(012) surface can elevate the Fermi level toward the conduction band, which is favorable for the occurrence of HER. Electrochemical computations are used to explore the mechanism of HER. It is found that, in most of Ni_n/α-Ga_2O_3 systems, the active sites of HER are on Ni_n clusters. Loading Ni_n clusters not only importantly reduces the Gibbs free energy of HER but also improves the reaction activity of surface O and Ga sites in HER. Our calculations reasonably explain the experimental observation on significant enhancement of activity for generating hydrogen after loading nickel oxide cocatalysts.展开更多
Novel Nb2O5 nanorods and polygonal Nb2O5 platelets were generated by a simple solvothermal technique. The geometry evolution of the resultant Nb2O5 from amorphous nanoparticles to crystallized particles, from polygona...Novel Nb2O5 nanorods and polygonal Nb2O5 platelets were generated by a simple solvothermal technique. The geometry evolution of the resultant Nb2O5 from amorphous nanoparticles to crystallized particles, from polygonal platelets to well-elongated nanorods was been studied in detail. The processing parameters, including the reaction temperature, reaction time, concentration of the precursors, and pH value of the solution, which affect the shape and size of the nanorods, were investigated. The Nb2O5 nanorods with different aspect ratios were examined by XRD, SEM and TEM. The experimental results show that Nb2O5 nanorod is the orthorhombic structure and well-crystallized. The growth of the nanorods follows their [001] direction. The successful generation of high quality Nb2O5 nanorods is not only important for transition metal oxide research, but also potentially important for further formation of new Nb-based 1-D nanostructures, such as NbS2 and NbN.展开更多
In this study, BaTiO3 （BTO）-doped YBCO films are prepared on LaA103 （100） single-crystal substrates by metal- organic decomposition （MOD） using trifluoroacetate （TFA） precursor solutions. The critical current ...In this study, BaTiO3 （BTO）-doped YBCO films are prepared on LaA103 （100） single-crystal substrates by metal- organic decomposition （MOD） using trifluoroacetate （TFA） precursor solutions. The critical current density （Jc） of BTO/YBCO film is as high as 10 MA/cm2 （77 K, 0 T）. The BTO peak is found in the X-ray diffraction （XRD） pattern of a final YBCO superconductivity film. Moreover, a comprehensive study of the precursor evolution is conducted mainly by X-ray analysis and μ-Raman spectroscopy. It is found that the TFA begins to decompose at the beginning of the thermal process, and then further decomposes as temperature increases, and at 700 ℃ BTO nanoparticles begin to appear. It sug- gests that the YBCO film embedded with BTO nanoparticles, whose critical current density （Jc） is enhanced, is successfully prepared by an easily scalable chemical solution deposition technique.展开更多
A series of Cd1-xZnxS/K2La2Ti3O10 composites were synthesized via a simple co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), X-ray energy di...A series of Cd1-xZnxS/K2La2Ti3O10 composites were synthesized via a simple co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), X-ray energy dispersive spectroscopy(EDX), ultraviolet-visible diffuse reflection(UV-Vis), X-ray photoelectron spectroscopy(XPS) and photoluminescence(PL) measurements. The composite structures consisted of Cd1-xZnxS nanoparticles evenly distributed on the surface of K2La2Ti3O10. The absorption edge of K2La2Ti3O10 shifted to the visible light region upon introduction of the Cd1-xZnxS nanoparticles. The photocatalytic activities of the catalysts were evaluated by hydrogen production under visible light irradiation. The prepared Cd0.8Zn0.2S(30wt%)/K2La2Ti3O10 exhibited higher photocatalytic activity, evolving 6.92 mmol/g H2 under visible light irradiation for 3 h. The promoted photocatalytic activity of the composites was attributed to the synergistic effect between Cd1-xZnxS and K2La2Ti3O10, which resulted in enhanced separation of photogenerated electrons and holes.展开更多
CdS/NiS nanocomposites were synthesized by electrochemical method. Ni and Cd is one of the important II-VI semiconducting materials with a direct band gap of 3.26 eV which finds applications in electrical conductivity...CdS/NiS nanocomposites were synthesized by electrochemical method. Ni and Cd is one of the important II-VI semiconducting materials with a direct band gap of 3.26 eV which finds applications in electrical conductivity and photo-catalysis. The synthesized nanocomposites were characterized by BET, UV-VIS, XRD, FE-SEM (EDAX) techniques. X-Ray diffraction (XRD) reveals crystallite size to be 23.22 nm which was calculated using Williamson-Hall (W-H) plot method. The energy of the band gap for CdS/NiS could be thus estimated to be 3.26 eV. The photocatalytic activity of the sample was evaluated by the degradation of textile dye methylene Blue (MB) in aqueous solutions under UV radiation. Hydrogen energy is regarded as a promising alternative in terms of energy conversion and storage. Hydrogen Evolution Reaction (HER) was carried out in both visible light and UV light by using Hydrazine (N<sub>2</sub>H<sub>4</sub>H<sub>2</sub>O) in the presence of CdS/NiS nanocomposite. The synthesized photocatalyst shows applicable performance for kinetics of Hydrogen Evolution Reaction (HER) in Visible light and UV light. The decomposition of hydrazine (N<sub>2</sub>H<sub>4</sub>H<sub>2</sub>O) proceeded rapidly to generate free hydrogen rich gas through OH radical contact with CdS/NiS nanocomposite at room temperature. The rate of HER is limited by either proton adsorption onto an active site or evolution of formed hydrogen from the surface. A high Tafel slope is indicative of proton adsorption as the rate limiting step, while a lower Tafel slope (20 - 45 mV) indicates that the evolution of molecules hydrogen from the catalyst is rate limiting. In the present case the Tafel slopes for visible light 23.5 mV and 42.5 mV for UV light. Blank experiments show poor activity for HER <em>i.e.</em> 10.1 - 13.5 mV.展开更多
We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_（8＋δ）（Bi2212） superconductor in the superconducting and pseudogap states by super-high resolution laser-based an...We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_（8＋δ）（Bi2212） superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212（T_c= 91 K） at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form（cos（2Φ））. It can be alternatively fitted by including a high-order term（cos（6Φ）） in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_（6＋δ） superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.展开更多
基金CONACYT (CB-2014-237049, PDCPN-2015-487 and Ph. D. scholarship 635249) for the financial support
文摘K2Ti6O13 whiskers were synthesized by conventional sol-gel method, sono-chemical assisted and microwave assisted sol-gel method in order to obtain catalysts with different particle sizes and to modify their optical, textural and electrochemical properties. These modifications improved their photocatalytic activity for H2 evolution and CO2 photo-reduction. Long K2Ti6O13 whiskers prepared by ultrasound assisted sol-gel method are the most active photocatalysts for the hydrogen evolution reaction using pure water as reactant (U-SG, 10,065 μmol g^-1). In contrast, an opposite behavior was observed using a mixture of ethanol-water, where the highest activity was achieved by the shortest and less crystalline K2Ti6O13 whiskers (C-SG, 3,2871 μmol g^-1). In case of CO2 photo-reduction, long whiskers that were also prepared by the sono-chemical assisted sol-gel method were the most active to transform CO2 to formaldehyde, methane, methanol and hydrogen. The EFB value of this catalyst is located very close to the potential for formaldehyde production and favors the selectivity to this organic product.
文摘A spinel oxide NiCo204 prepared by thermal decomposition is of very high activity for the oxygen evolution reaction(OER)in alkaline solution.The oxygen evolution overpotential on NiCo204 is 0.252-0.262V in 10 M NaOH solution at 343K and current density 100 mAcm^(-2).
基金the funding support from the National Natural Science Foundation of China(51722404,51674177,51804221 and 91845113)the National Key R&D Program of China(2018YFE0201703)+2 种基金the China Postdoctoral Science Foundation(2018M642906 and 2019T120684)the Fundamental Research Funds for the Central Universities(2042017kf0200)the Hubei Provincial Natural Science Foundation of China(2019CFA065)。
文摘Implementation of non-precious electrocatalysts is key-enabling for water electrolysis to relieve challenges in energy and environmental sustainability. Self-supporting Ni-V2O3 electrodes consisting of nanostrip-like V2O3 perpendicularly anchored on Ni meshes are herein constructed via the electrochemical reduction of soluble NaVO3 in molten salts for enhanced electrocatalytic hydrogen evolution. Such a special configuration in morphology and composition creates a well confined interface between Ni and V2O3. Experimental and Density-Functional-Theory results confirm that the synergy between Ni and V2O3 accelerates the dissociation of H2O for forming hydrogen intermediates and enhances the combination of H*for generating H2.
基金supported by the National Natural Science Foundation of China (51602128)the Research Foundation from University of Jinan (XKY1401, XBS1508, XBH1504)。
文摘Development of high efficient and stable water oxidation catalysts is essential for the realization of industrial water-splitting systems. Herein, a novel approach involving an in-situ transformation of Co(OH)2 nanosheets into NH4 CoPO4·H2 O nanoplates on Co foil is reported. As a 3 D self-supported oxygen revolution reaction(OER) electrocatalyst, the as-prepared NH4 CoPO4·H2 O/Co exhibits remarkable catalytic activity and exceptional stability. Specifically, it can deliver a current density of 10 m A cm^(-2) at a quite low overpotential of 254 m V with a small Tafel slope of 64.4 m V dec-1 in alkaline electrolyte. Through experimental study and theoretical analysis, the excellent OER performance can be attributed to enriched exposed active sites, favorable electron/proton transfer and mass transport, and its unique asymmetric local atomic and electronic structure. Thus, this present research not only provides a practicable in-situ transformation strategy to design 3 D self-supported electrocatalysts, but also enlightens a new way of developing transition-metal phosphates for efficient and stable water oxidation at atomic level.
文摘Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr3Fe2O7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge disproportionation of Fe4+, the OER activity of Sr3Fe2O7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe4+. When metal substitution was made to Sr3Fe2O7 for stabilizing Fe4+ at room temperature, the temperature dependence of the OER activity disappeared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe4+ is substantially important for achieving high OER activity.
基金supported by the "Strategic Priority Research Program" of the Chinese Academy of Sciences (XDA02040600)supported by the Canadian Foundation for Innovation+5 种基金Natural Sciences and Engineering Research Council of Canadathe University of Saskatchewanthe Government of SaskatchewanWestern Economic Diversification Canadathe National Research Council Canadathe Canadian Institutes of Health Research
文摘To accelerate the kinetics of oxygen evolution reaction(OER)regarding the energy conversion and storage approaches,the discovery of desirable cost-effective and highly efficient electrocatalysts is of prime importance.This study demonstrates a layered CaCo_2O_4with a two-dimensional nanoplate structure,which possesses electrocatalytic activity for OER.The OER activity was achieved on CaCo_2O_4with a Tafel slope of 71 mV dec^(-1)and a current density of 10 mA cm^(-2)at an overpotential of 371 mV,which was more active than the similar structure LiCoO_2catalyst.Combined with X-ray absorption fine structure and density functional theory calculations,the enhanced OER activity and stability are mainly attributed to the unique electronic structure derived from the interaction of Ca and Co,and improved electrical conductivity.CaCo_2O_4can be developed as a highly active and earth-abundant catalyst for OER in energy conversion and storage technologies.
文摘Physiological changes in the photosynthesis, respiration and cell division of Chlamydomonas reinhardtii, a freshwater green alga, in response to adenine nucleotides were investigated. In advance of this investigation, two adenine nucleotides, di(2'-O-methyl)-cyclic bis(3'-5')diadenylic acid (1) and its N-benzoyl-protected analog 2 were synthesized from the commercially available adenosine phosphoramidite. The respective analogs significantly promoted the cell division (cell number) of C. reinhardtii strains 137c mt+ and BR mt+. Moreover, they significantly enhanced the O2 evolution (photosynthesis) and O2 uptake (respiration) of both strains. c-di-AMP analogs seem to play an effective role as a physiological activator in planta.
基金financially supported by the National Natural Science Foundation of China under Grants 21473183 and 21303079
文摘In the semiconductor-based photocatalysts for overall water splitting, loading proper cocatalysts play a crucial role in enhancing the photocatalytic activity. In this work, we have chosen Ni_n/α-Ga_2O_3 as a model and provided detailed density functional theory calculations to investigate the function of cocatalysts in hydrogen evolution reaction(HER). We have studied the formation and stability of Ni_n(n = 1–4) cluster on two stable surfaces of α-Ga_2O_3(001) and(012). In a Ni_n/α-Ga_2O_3 system, as the Ni 3d states well overlap with O and Ga states, the excited electrons transferred from Ga to Ni may participate in HER. We theoretically predict that introduction of Nincluster on(012) surface can elevate the Fermi level toward the conduction band, which is favorable for the occurrence of HER. Electrochemical computations are used to explore the mechanism of HER. It is found that, in most of Ni_n/α-Ga_2O_3 systems, the active sites of HER are on Ni_n clusters. Loading Ni_n clusters not only importantly reduces the Gibbs free energy of HER but also improves the reaction activity of surface O and Ga sites in HER. Our calculations reasonably explain the experimental observation on significant enhancement of activity for generating hydrogen after loading nickel oxide cocatalysts.
基金Funded by the International Cooperation Project of Hubei Province (2006CA014)
文摘Novel Nb2O5 nanorods and polygonal Nb2O5 platelets were generated by a simple solvothermal technique. The geometry evolution of the resultant Nb2O5 from amorphous nanoparticles to crystallized particles, from polygonal platelets to well-elongated nanorods was been studied in detail. The processing parameters, including the reaction temperature, reaction time, concentration of the precursors, and pH value of the solution, which affect the shape and size of the nanorods, were investigated. The Nb2O5 nanorods with different aspect ratios were examined by XRD, SEM and TEM. The experimental results show that Nb2O5 nanorod is the orthorhombic structure and well-crystallized. The growth of the nanorods follows their [001] direction. The successful generation of high quality Nb2O5 nanorods is not only important for transition metal oxide research, but also potentially important for further formation of new Nb-based 1-D nanostructures, such as NbS2 and NbN.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51002149 and 51272250)the National Basic Research Program of China(Grant No.2011CBA00105)
文摘In this study, BaTiO3 （BTO）-doped YBCO films are prepared on LaA103 （100） single-crystal substrates by metal- organic decomposition （MOD） using trifluoroacetate （TFA） precursor solutions. The critical current density （Jc） of BTO/YBCO film is as high as 10 MA/cm2 （77 K, 0 T）. The BTO peak is found in the X-ray diffraction （XRD） pattern of a final YBCO superconductivity film. Moreover, a comprehensive study of the precursor evolution is conducted mainly by X-ray analysis and μ-Raman spectroscopy. It is found that the TFA begins to decompose at the beginning of the thermal process, and then further decomposes as temperature increases, and at 700 ℃ BTO nanoparticles begin to appear. It sug- gests that the YBCO film embedded with BTO nanoparticles, whose critical current density （Jc） is enhanced, is successfully prepared by an easily scalable chemical solution deposition technique.
基金Funded by the National Natural Science Foundation of China(Nos.51202056,51372068)Hebei Natural Science Funds for Distinguished Young Scholar(No.B2014209304)+1 种基金Hebei Provincial Foundation for International Cooperation(No.15391403D)Hebei Natural Science Funds for the Joint Research of Iron and Steel(No.B2014209314)
文摘A series of Cd1-xZnxS/K2La2Ti3O10 composites were synthesized via a simple co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), X-ray energy dispersive spectroscopy(EDX), ultraviolet-visible diffuse reflection(UV-Vis), X-ray photoelectron spectroscopy(XPS) and photoluminescence(PL) measurements. The composite structures consisted of Cd1-xZnxS nanoparticles evenly distributed on the surface of K2La2Ti3O10. The absorption edge of K2La2Ti3O10 shifted to the visible light region upon introduction of the Cd1-xZnxS nanoparticles. The photocatalytic activities of the catalysts were evaluated by hydrogen production under visible light irradiation. The prepared Cd0.8Zn0.2S(30wt%)/K2La2Ti3O10 exhibited higher photocatalytic activity, evolving 6.92 mmol/g H2 under visible light irradiation for 3 h. The promoted photocatalytic activity of the composites was attributed to the synergistic effect between Cd1-xZnxS and K2La2Ti3O10, which resulted in enhanced separation of photogenerated electrons and holes.
文摘CdS/NiS nanocomposites were synthesized by electrochemical method. Ni and Cd is one of the important II-VI semiconducting materials with a direct band gap of 3.26 eV which finds applications in electrical conductivity and photo-catalysis. The synthesized nanocomposites were characterized by BET, UV-VIS, XRD, FE-SEM (EDAX) techniques. X-Ray diffraction (XRD) reveals crystallite size to be 23.22 nm which was calculated using Williamson-Hall (W-H) plot method. The energy of the band gap for CdS/NiS could be thus estimated to be 3.26 eV. The photocatalytic activity of the sample was evaluated by the degradation of textile dye methylene Blue (MB) in aqueous solutions under UV radiation. Hydrogen energy is regarded as a promising alternative in terms of energy conversion and storage. Hydrogen Evolution Reaction (HER) was carried out in both visible light and UV light by using Hydrazine (N<sub>2</sub>H<sub>4</sub>H<sub>2</sub>O) in the presence of CdS/NiS nanocomposite. The synthesized photocatalyst shows applicable performance for kinetics of Hydrogen Evolution Reaction (HER) in Visible light and UV light. The decomposition of hydrazine (N<sub>2</sub>H<sub>4</sub>H<sub>2</sub>O) proceeded rapidly to generate free hydrogen rich gas through OH radical contact with CdS/NiS nanocomposite at room temperature. The rate of HER is limited by either proton adsorption onto an active site or evolution of formed hydrogen from the surface. A high Tafel slope is indicative of proton adsorption as the rate limiting step, while a lower Tafel slope (20 - 45 mV) indicates that the evolution of molecules hydrogen from the catalyst is rate limiting. In the present case the Tafel slopes for visible light 23.5 mV and 42.5 mV for UV light. Blank experiments show poor activity for HER <em>i.e.</em> 10.1 - 13.5 mV.
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0300300the National Natural Science Foundation of China under Grant No 11334010+1 种基金the National Basic Research Program of China under Grant No2015CB921300the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB07020300
文摘We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_（8＋δ）（Bi2212） superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212（T_c= 91 K） at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form（cos（2Φ））. It can be alternatively fitted by including a high-order term（cos（6Φ）） in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_（6＋δ） superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.
