Electrodeposition And Photoelectrochemical Performance Of 3D Cuprous Oxide Photocathode For Solar Water Splitting

Solar water splitting is identified as an effective way to deal with the problems of energy crisis and environmental pollution.In recent decades,lots of researchers have devoted intense investigations in this area and various semiconductor materials have been exploited and applied in the fabrication of photoelectrodes.With its small bandgap that is very favored for the solar water splitting reaction,Cu₂O have attracted high attention from researchers.Cu₂O is an intrinsic p-type semiconductor with a direct bandgap of 2.2 eV that straddles the water reduction potential and water oxidation potential which determines Cu₂O an ideal material for photocathode.However,the notorious drawback of photocorrosion has severely confined the application of Cu₂O in solar water splitting.At the same time,the mismatch between the light absorption depth and the carrier diffusion length has limited the promotion in the light conversion efficiency of Cu₂O.This study focuses on the preparation of Cu₂O photocathode,introducing 3D Cu micro-cone arrays into the fabrication process.By electrodepositing Cu₂O onto the Cu micro-cone arrays,we acquire 3D Cu₂O photocathode,which possesses superior property than the planar configuration.To solve the problem of photocorrosion,this study has applied different techniques to protect the 3D Cu₂O photocathode,designing a series of protection schemes and finding out the most effective one.The properties of Cu₂O photocathode are studied by a sequence of photoelectrochemical tests.The main investigation aspects are listed below:3D Cu micro-cone arrays are prepared by chemical deposition.The Cu cones which possess the length of 5?m and root diameter of 1?m are the most suitable to be used in the fabrication of 3D Cu₂O photocathode.3D Cu₂O photocathode is prepared by growing Cu₂O grains onto 3D Cu micro-cone arrays using electrodeposition.The best parameters for the fabrication of the 3D and planar Cu₂O photocathodes are respectively 0.6 mA cm^-2,60min and 0.3 mA cm^-2,90 min.The carrier density and flat band potential of the 3D Cu₂O photocathode are respectively 1.13×10¹⁸ cm^-3 and0.49 V.The 3D and planar Cu₂O photocathodes possesses the same visible light absorption and conversion capability,which reaches its peak at the wave length of 425 nm.Cu₂O of the photocathode is reduced to Cu in the potential range of-0.4 V^-1.67 V vs.Ag/AgCl sat.and cannot be oxidized when the potential increases again.The 3D Cu₂O photocathode exhibits better performance than the planar Cu₂O photocathode.This is mainly because that the 3D structure possesses much larger surface area and better light absorption capability than the planar structure.At the same time,the 3D structure can resolve the problem of mismatch between the light absorption depth and carrier diffusion length.Atomic layer deposition is demonstrated to be the most effective method for the protection of the 3D Cu₂O photocathode and 20 nm ZnO+10 nm TiO₂+Pt nanoparticles is proven to be the most effective protection scheme.The protected 3D Cu₂O photocathode is more stable than the bare 3D Cu₂O photocathode.Surface components of the protected 3D Cu₂O photocathode include ZnO,TiO₂,Pt and Cu₂O.We still need to improve our skill in the atomic layer deposition and cocatalyst deposition in order to improve the property of the protected 3D Cu₂O photocathode.