Owing to the growing consumption of non-renewable resources and increased environmental pollution,significant attention has been directed toward developing renewable and environmentally friendly energy sources.Hydroge...Owing to the growing consumption of non-renewable resources and increased environmental pollution,significant attention has been directed toward developing renewable and environmentally friendly energy sources.Hydrogen has emerged as a clean energy carrier and is considered an ideal chemical for power generation via fuel cells.Using renewable energy to power hydrogen production is an attractive prospect,and hydrogen production through photoelectrochemical water splitting is considered a promising area of interest;consequently,significant research is being conducted on rationally designed photoelectrodes.Generally,a photocathode for hydrogen evolution must have a conduction band that is more negative than the reduction potential of hydrogen.Numerous photocathode materials have been developed based on this premise;these include p-Si,InP,and GaN.Compared with other photocathode materials,Cu-based compounds are advantageous owing to their low preparation costs and diverse chemical states.For example,Cu_(2)O is a non-toxic p-type metal oxide semiconductor material with an appropriate band structure for water splitting and a direct band gap of 1.9-2.2 eV.Furthermore,the production of Cu_(2)O is facile,and the required materials are abundant;thus,it has attracted significant interest as a material for photocathodes.However,Cu_(2)O suffers from rapid recombination of photogenerated carriers and severe photo-corrosion,leading to unsatisfactory efficiency and poor stability.Intrinsically,the poor photo-stability of Cu_(2)O can be attributed to the location of the redox potential of Cu_(2)O within its bandgap,owing to which photoelectrons tend to preferentially reduce Cu_(2)O to Cu rather than reduce water to reduction.Therefore,Cu_(2)O itself is not an ideal hydrogen evolution catalyst.Thus,co-catalysts are necessary to improve its hydrogen evolution activity and photostability.In addition to co-catalysts,combining Cu_(2)O with tailored n-type semiconductors to generate built-in electric fields of p-n junctions has attracted extensive attention owing to its ability of increasing the separation of photogenerated carriers.Similarly,applying a hole transfer layer on the substrate can promote photocarrier separation.Furthermore,considering that water is indispensable for Cu_(2)O reduction,one effective approach to improve the stability of Cu_(2)O is the addition of a protective/passivation layer to isolate Cu_(2)O from water in aqueous electrolytes.In this review,we provide a brief overview of the mechanism of photoelectrochemical water splitting and the band structure of Cu_(2)O ;preparation methods of Cu_(2)O photocathodes;strategies to improve the efficiency and stability of Cu_(2)O photocathodes,including the construction of p-n junctions,integration with co-catalysts,and modifications using hole transport layers;advanced photoelectrochemical characterization techniques;and a discussion regarding the direction of future photocathode research.展开更多
In this paper a negative electron affinity （NEA） multialkali photocathode of （Na<sub>2</sub>KSb-Cs）-O-Cs structure is fabricated by new technology. It is found that its emission stability is much bette...In this paper a negative electron affinity （NEA） multialkali photocathode of （Na<sub>2</sub>KSb-Cs）-O-Cs structure is fabricated by new technology. It is found that its emission stability is much better than that of the NEA GaAs photocathode, but is inferior to that of the conventional Na<sub>2</sub>KSb（Cs）. After 70 hour performance in a pumping vacuum system, the emission sensitivity of the NEA （Na<sub>2</sub>KSb-Cs）-O-Cs photocathode drops only by 2.5%. The emission stability is closely related to the states of the activation cesium and oxygen during activation, best results being obtained with cesium ions and excited oxygen. Furthermore, better photoemission sensitivity and emission stability may be obtained if the cathode is illuminated by intense white light during the activation process. The performance of the NEA （Na<sub>2</sub>KSb-Cs）-O-Cs cathode which has not been illuminated by intense white light during activation may be improved by the illumination even during operation intermission.展开更多
The utilization of solar energy for hydrogen production via water splitting has garnered considerable attention in the realm of renewable energy.Si nanowires photocathodes own the advantages of effective photon absorp...The utilization of solar energy for hydrogen production via water splitting has garnered considerable attention in the realm of renewable energy.Si nanowires photocathodes own the advantages of effective photon absorption,non toxicity and industrial applicability.Nevertheless,the photoelectrocatalytic(PEC)performance of Si nanowires photocathodes is still limited by ineffective or deficient active sites on their surfaces.Here,we develop an efficient Si based photocathode modified with Al-porphyrin-based MOF(Al-PMOF),consisted of an earth-abundant metal containing Al(OH)O_(4) cluster bridged by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin.The assembled Al-PMOF significantly enhances the photocurrent density of bare Si nanowires photocathodes,resulting in a twofold increase under equivalent conditions,alongside a positive shift of 200 mV in the onset potential of the Si/Al-PMOF photocathode.The improved PEC hydrogen evolution performance is ascribed to accelerate surface charge transfer of Si photocathode and provision of favorable active site for the hydrogen evolution reaction.This work provides insights into the fabrication of semiconductor/molecule catalyst hybrid photocathodes,thus facilitating the realization of high-efficiency PEC water splitting.展开更多
文摘Owing to the growing consumption of non-renewable resources and increased environmental pollution,significant attention has been directed toward developing renewable and environmentally friendly energy sources.Hydrogen has emerged as a clean energy carrier and is considered an ideal chemical for power generation via fuel cells.Using renewable energy to power hydrogen production is an attractive prospect,and hydrogen production through photoelectrochemical water splitting is considered a promising area of interest;consequently,significant research is being conducted on rationally designed photoelectrodes.Generally,a photocathode for hydrogen evolution must have a conduction band that is more negative than the reduction potential of hydrogen.Numerous photocathode materials have been developed based on this premise;these include p-Si,InP,and GaN.Compared with other photocathode materials,Cu-based compounds are advantageous owing to their low preparation costs and diverse chemical states.For example,Cu_(2)O is a non-toxic p-type metal oxide semiconductor material with an appropriate band structure for water splitting and a direct band gap of 1.9-2.2 eV.Furthermore,the production of Cu_(2)O is facile,and the required materials are abundant;thus,it has attracted significant interest as a material for photocathodes.However,Cu_(2)O suffers from rapid recombination of photogenerated carriers and severe photo-corrosion,leading to unsatisfactory efficiency and poor stability.Intrinsically,the poor photo-stability of Cu_(2)O can be attributed to the location of the redox potential of Cu_(2)O within its bandgap,owing to which photoelectrons tend to preferentially reduce Cu_(2)O to Cu rather than reduce water to reduction.Therefore,Cu_(2)O itself is not an ideal hydrogen evolution catalyst.Thus,co-catalysts are necessary to improve its hydrogen evolution activity and photostability.In addition to co-catalysts,combining Cu_(2)O with tailored n-type semiconductors to generate built-in electric fields of p-n junctions has attracted extensive attention owing to its ability of increasing the separation of photogenerated carriers.Similarly,applying a hole transfer layer on the substrate can promote photocarrier separation.Furthermore,considering that water is indispensable for Cu_(2)O reduction,one effective approach to improve the stability of Cu_(2)O is the addition of a protective/passivation layer to isolate Cu_(2)O from water in aqueous electrolytes.In this review,we provide a brief overview of the mechanism of photoelectrochemical water splitting and the band structure of Cu_(2)O ;preparation methods of Cu_(2)O photocathodes;strategies to improve the efficiency and stability of Cu_(2)O photocathodes,including the construction of p-n junctions,integration with co-catalysts,and modifications using hole transport layers;advanced photoelectrochemical characterization techniques;and a discussion regarding the direction of future photocathode research.
基金This work is supported by the Natural Science Foundation of Fujian Province, China.
文摘In this paper a negative electron affinity （NEA） multialkali photocathode of （Na<sub>2</sub>KSb-Cs）-O-Cs structure is fabricated by new technology. It is found that its emission stability is much better than that of the NEA GaAs photocathode, but is inferior to that of the conventional Na<sub>2</sub>KSb（Cs）. After 70 hour performance in a pumping vacuum system, the emission sensitivity of the NEA （Na<sub>2</sub>KSb-Cs）-O-Cs photocathode drops only by 2.5%. The emission stability is closely related to the states of the activation cesium and oxygen during activation, best results being obtained with cesium ions and excited oxygen. Furthermore, better photoemission sensitivity and emission stability may be obtained if the cathode is illuminated by intense white light during the activation process. The performance of the NEA （Na<sub>2</sub>KSb-Cs）-O-Cs cathode which has not been illuminated by intense white light during activation may be improved by the illumination even during operation intermission.
基金Project(22078368)supported by the National Natural Science Foundation of China。
文摘The utilization of solar energy for hydrogen production via water splitting has garnered considerable attention in the realm of renewable energy.Si nanowires photocathodes own the advantages of effective photon absorption,non toxicity and industrial applicability.Nevertheless,the photoelectrocatalytic(PEC)performance of Si nanowires photocathodes is still limited by ineffective or deficient active sites on their surfaces.Here,we develop an efficient Si based photocathode modified with Al-porphyrin-based MOF(Al-PMOF),consisted of an earth-abundant metal containing Al(OH)O_(4) cluster bridged by 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin.The assembled Al-PMOF significantly enhances the photocurrent density of bare Si nanowires photocathodes,resulting in a twofold increase under equivalent conditions,alongside a positive shift of 200 mV in the onset potential of the Si/Al-PMOF photocathode.The improved PEC hydrogen evolution performance is ascribed to accelerate surface charge transfer of Si photocathode and provision of favorable active site for the hydrogen evolution reaction.This work provides insights into the fabrication of semiconductor/molecule catalyst hybrid photocathodes,thus facilitating the realization of high-efficiency PEC water splitting.
