Study On Improvement Of Photoelectrochemical Properties Of Cuprous Oxide Photocathode By Surface Modification

Hydrogen energy is an important component of the future national energy system,and photoelectrocatalytic（PEC）water splitting is a promising technology for green hydrogen preparation.The development of low-cost,highly active and stable photoelectrodes has important research value and practical significance,and has received wide attention from the academic community of energy catalysis.Cuprous oxide（Cu₂O）is widely used in photocathodes due to its ideal band gap,suitable energy band position and high natural abundance.However,two major challenges,self-corrosion under light and photogenerated carrier recombination,have greatly limited its practical applications.Taking the problems of Cu₂O photocathode as the guide,in order to promote the practical application of photocatalytic water splitting technology,this project combines catalyst design and electrode interface design,mainly carried out in the following two aspects.（1）The electrode was prepared by directly anchoring titanium dioxide nanoparticles（P25）on the surface of Cu₂O film electrode using self-polymerized dopamine coating（PDA）,which exhibited good catalytic activity and stability as a photocathode.The phase and structure of the electrodes were identified with the help of various characterizations such as X-ray diffraction,X-ray photoelectron spectroscopy and atomic force microscopy.The feasibility of the preparation route and the superiority of the photoelectrode structure were discussed by various analyses such as UV-Vis spectroscopy and photoluminescence spectroscopy.It was shown that the surface modification of Cu₂O polyhedral films with the joint participation of P25nanoparticles and dopamine exhibited excellent modification effects.On the one hand,the P25 nanoparticles filled into the Cu₂O polyhedral gill well during the polymerization of dopamine,realizing the conformal assembly of dopamine on the Cu₂O polyhedral surface.The hydrophilicity of Cu₂O surface is effectively enhanced,and abundant reactant concentration is provided on the electrode surface,which tilts the reaction equilibrium towards reduction to H₂.On the other hand,the natural viscosity of PDA strengthens the solid interface of Cu₂O/TiO₂ p/n heterojunction,which leads to a large enhancement of carrier utilization.More importantly,the PDA layer on the surface of Cu₂O can effectively mitigate the photocorrosion of Cu₂O originating from soluble reactive groups in the electrolyte and effectively enhance the Cu₂O photocathode stability.（2）The porous MOFs material Cu₃（BTC）₂ was introduced to grow in situ on the Cu₂O photocathode surface by an active agent-free method.While two strategies were proposed for the poor conductivity of MOFs,which are the introduction of guest conductors（TCNQ）and carbonization of MOFs.The phase composition of the electrode was characterized by X-ray diffraction and Fourier transform infrared spectroscopy.And the photoresponse and conductivity of the photoelectrodes were analyzed by UV-Vis spectroscopy and electrochemical impedance spectroscopy.It was shown that Cu₃（BTC）₂ formed a protective layer and inhibited photocorrosion,thus enhancing the stability of the photoelectrode;the effective combination of Cu₂O and Cu₃（BTC）₂ improves the transfer efficiency of photogenerated electrons and promotes the carrier separation;the porous structure of MOFs leads to the expansion of specific surface area which significantly reduces the diffusion resistance of the electrode and thus promotes the catalytic reaction.However,the loading of TCNQ enhances the electrical conductivity of the electrode material,it also occupies the pores of MOFs,which hinders the light absorption ability of the electrode and reduces the specific surface area of the electrode;the C/Cu after the carbonization of Cu₃（BTC）₂ also enhances the electrical conductivity,but the MOFs-derived C layer is not sufficient to form a dense passivation layer and leads to the rapid deactivation of the electrode.