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
Based on the cyclic voltammogram(CV)of TiO_(2)/Ti electrodes in Cu^2+ion solution,we fabricated Cu2O and Cu particles onto TiO_(2)flat surfaces separately or simultaneously by adjusting the applied potentials during e...Based on the cyclic voltammogram(CV)of TiO_(2)/Ti electrodes in Cu^2+ion solution,we fabricated Cu2O and Cu particles onto TiO_(2)flat surfaces separately or simultaneously by adjusting the applied potentials during electrodeposition.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)showed that Cu2O and Cu have different growth modes:Cu2O particles crystallize on the TiO_(2)surface separately while Cu particles nucleate on previously grown particles,forming a stacked particle structure.This growth behavior can be explained by the different electron transfer behavior on the Cu2O/TiO_(2)and Cu/TiO_(2)interfaces and this is determined by their bandgap alignments.Compared with a pure TiO_(2)photoanode,a significant enhancement of the photocurrent was observed for both the Cu2O/TiO_(2)and Cu/TiO_(2)heterostructures.A potential region exists where Cu2O and Cu grow on the TiO_(2)surface simultaneously and the corresponding photocurrent is relatively stable and reaches a maximum.UV-Vis diffuse reflectance spectroscopy,electrochemical impedance spectroscopy(EIS),and photocurrent vs potential characteristics revealed that the visible light absorption by Cu20 and Cu contributes significantly to the photocurrent.Cu/TiO_(2)resulted in greater broadband visible light utilization during the photoelectric conversion.Additionally,the increased zero-current potential and the effective charge separation as well as the rapid carrier transfer on the electrode/electrolyte interface are also related to the enhanced photoelectrochemical properties.展开更多
Cu2O particles with different shapes were prepared via reducing Cu（II） in alkaline system by glucose at 50℃. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and tr...Cu2O particles with different shapes were prepared via reducing Cu（II） in alkaline system by glucose at 50℃. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. It is found that the shape of Cu2O particles changes with the change of concentration of NaOH. The different shapes of Cu2O particles are due to the absorption of OH- ions on Cu2O particles, which arise the variety of growth mode of Cu2O, and then influence the morphology of Cu2O particles.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.
文摘Based on the cyclic voltammogram(CV)of TiO_(2)/Ti electrodes in Cu^2+ion solution,we fabricated Cu2O and Cu particles onto TiO_(2)flat surfaces separately or simultaneously by adjusting the applied potentials during electrodeposition.Scanning electron microscopy(SEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)showed that Cu2O and Cu have different growth modes:Cu2O particles crystallize on the TiO_(2)surface separately while Cu particles nucleate on previously grown particles,forming a stacked particle structure.This growth behavior can be explained by the different electron transfer behavior on the Cu2O/TiO_(2)and Cu/TiO_(2)interfaces and this is determined by their bandgap alignments.Compared with a pure TiO_(2)photoanode,a significant enhancement of the photocurrent was observed for both the Cu2O/TiO_(2)and Cu/TiO_(2)heterostructures.A potential region exists where Cu2O and Cu grow on the TiO_(2)surface simultaneously and the corresponding photocurrent is relatively stable and reaches a maximum.UV-Vis diffuse reflectance spectroscopy,electrochemical impedance spectroscopy(EIS),and photocurrent vs potential characteristics revealed that the visible light absorption by Cu20 and Cu contributes significantly to the photocurrent.Cu/TiO_(2)resulted in greater broadband visible light utilization during the photoelectric conversion.Additionally,the increased zero-current potential and the effective charge separation as well as the rapid carrier transfer on the electrode/electrolyte interface are also related to the enhanced photoelectrochemical properties.
基金Project(50674100) supported by the National Nature Science Foundation of China
文摘Cu2O particles with different shapes were prepared via reducing Cu（II） in alkaline system by glucose at 50℃. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. It is found that the shape of Cu2O particles changes with the change of concentration of NaOH. The different shapes of Cu2O particles are due to the absorption of OH- ions on Cu2O particles, which arise the variety of growth mode of Cu2O, and then influence the morphology of Cu2O particles.
