Preparation And PEC Performance Study Of Cu₂O And Sb₂S₃ Based Photocathodes

With the growing shortage of fossil fuels and the increasing greenhouse effect,the research task of vigorously developing hydrogen energy to replace fuels is imminent.And solar energy is the only inexhaustible energy source in nature.Converting solar energy into hydrogen energy is an effective way to alleviate the energy crisis and environmental pollution.Photoelectrochemical water splitting is one of the solar to hydrogen conversion methods,which is more advantageous than traditional photocatalysis.Photo-generated carriers were excited by absorbed photons and transferred to the photocathode/electrolyte interface for water splitting.The most important part of the photoelectrochemical cell is materials of the photoelectrode.Finding a low-cost,high-efficiency semiconductor for water splitting is a hard task.Taking the search for a suitable semiconductor as the light-absorbing material of the photocathode as the research direction,this paper attempts to improve the PEC performance of Cu₂O by nanocrystallization,homojunction construction,load of a precious metal layer and so on.Besides,we explore a new application of antimony sulfide semiconductor in the field of photoelectrocatalytic water splitting.The main contents include:1.We prepared Cu₂O nanorods/film structures by chemical bath deposition,anodization method,electrochemical deposition and thermal oxidation method.After comparing and analyzing the advantages and disadvantages of each preparation method,it is easier to control the surface morphology of cuprous oxide nanorods without other phases and obtain a smaller dark-current by anodization method.In terms of fabricating thin film structures,it costs less reaction energy consumption and it is easier to obtain uniform thin film thickness,which is suitable for device preparation.we prefer to choose anodization method and electrochemical deposition method to prepare the cuprous oxide in the subsequent work.2.A cuprous oxide nanorods homo-junction photocathode was prepared by anodic oxidation and electrochemical deposition method.We utilized cuprous oxide nanorod structure and the method of constructing a homojunction to alleviate the contradiction between the diffusion length of minority carrier and the depth of light absorption and improve the efficiency of carrier separation.And we discussed the effects of the n-type cuprous oxide particles with specific exposed crystal planes and the p-type cuprous oxide barrier layer.It was confirmed that the photocurrent density of the Cu₂O NRs homojunction photoelectrode was 3.6 times higher than that of the pure cuprous oxide photoelectrode,and the introduction of p-type cuprous oxide barrier layer effectively reduces the dark current.3.We prepared the more stable cuprous oxide film photocathode with the load of a dense platinum layer on the surface and an ultra-thin gold layer on the back.The dense platinum layer loaded on the surface of the photocathode can be used as both a hydrogen production promoter and an electrode protection layer,which improved the stability of the cuprous oxide photocathode.And the SPR effect of the ultra-thin gold layer is used to improve the efficiency of light absorption.In addition,an unassisted solar water-splitting device consisted of this cuprous oxide based photocathode and a bismuth vanadate based photoanode was successfully achieved a photocurrent density of 0.1mA cm^-2 in a weak acid solution?pH=6.0?.4.For the first time,we prepared Sb₂S₃/CdS/TiO₂/Pt photocathode with antimony sulfide film as light absorption layer.Untilizing the anisotropic electric conductivity of antimony sulfide semiconductor,we prepared high-quality and repeatable[hk1]-oriented antimony sulfide film based photocathodes.Sb₂S₃/CdS/TiO₂ photocathodes yielded a record-high photocurrent density of-6.0 mA cm^-2 at 0 V_RHE in a near-neutral electrolyte?pH=6.0?and an onset potential of+0.5 V_RHE.Besides,it could maintain92%of initial photocurrent density after the continuous stability testing of 60 min.This is the most excellent performance obtained in the reported works.