Development Of BiVO₄-based Photoelectrode Materials And Their Photoelectric Water Splitting And Photocathode Anticorrosion Properties

Facing the increasingly severe energy shortage and metal corrosion problems,it is urgent to explore new energy development and metal protection technologies.Semiconductor photocatalytic water splitting can use solar energy to decompose water into H₂ and O₂ to obtain hydrogen energy.Semiconductor photocathode anticorrosion technology not only uses solar energy to split water to obtain hydrogen energy,but also induces photo-generated electrons to transfer to the protected metal surface,effectively avoiding metal dissolution.It provides an effective means for mankind to solve the energy crisis and metal corrosion problems.However,the semiconductor light absorption range is narrow,the carrier recombination rate is faster,and the interface charge transfer is slow,which leads to the weaker performance of semiconductor photocatalytic water decomposition and photocathode anticorrosion.In response to these problems,this thesis takes the carrier separation and the precise control of the interfacial water oxidation reaction kinetics as ideas to carry out the development of the BiVO₄/cocatalyst photoelectrode system and the research of photoelectrocatalytic water oxidation and photocathodic protection of 304 stainless steel（304SS）.In this study,the precise design of BiVO₄/cocatalyst structure-the catalytic conversion mechanism of interfacial water molecules is the main line,and the interaction between the photoelectrode’s photoelectrochemical water splitting and photocathode cathodic protection performance and the composition and microstructure of each component is deeply explored.The main research contents of this paper are as follows:1.The citric acid complex method is used to uniformly grow an amorphous FeOOH promoter on the surface of BiVO₄,which significantly improves the quality of the BiVO₄/FeOOH electrode interface.Compared with the BiVO₄ electrode,the BiVO₄/FeOOH（citrate）photoelectrode generates a photocurrent density of 3.33m A·cm^-2under a bias voltage of 1.23 V vs.RHE,which improves the oxidation rate of water at the electrode interface.Studies have shown that as a grafting unit,citrate can anchor FeOOH firmly on the BiVO₄ interface,realize the effective separation of interface electrons/holes,inhibit the growth of FeOOH nanoparticles,and provide abundant oxygen vacancies to promote Oxidation of water.The accumulated charge of the BiVO₄/FeOOH（citrate）photoelectrode is 2-20 times that of BiVO₄,indicating that a uniform FeOOH coating can effectively store photo-generated holes and increase the potential drop in the Helmholtz layer,thereby promoting the formation of interface holes transfer and water oxidation.s2.Through the cyclic voltammetric electrodeposition method,oxygen holes were introduced on the surface of BiVO₄,and the CoP promoter was successfully loaded.The introduction of oxygen vacancies and CoP loads by cyclic voltammetry increased the carrier transfer efficiency of BiVO₄ by 2.9 times,and the carrier separation efficiency reached 68.2%,which increased the water oxidation reaction rate,thereby inhibiting photo-generated electron-holes the recombination rate,and a photocurrent density of 2.14 m A·cm^-2 under 1.23 V vs.RHE.Although the introduction of oxygen vacancies and CoP promoters improves the water oxidation kinetics of BiVO₄photoelectrodes,the electrodes are prone to photo-corrosion under external bias,and the electrode stability is low,which is not conducive to long-term water decomposition applications.For this reason,this section explores the application of photocathode anti-corrosion under unbiased conditions.The open circuit potential of the BiVO₄/CoP（CV）photoelectrode shifted negatively by 240 m V,and the corrosion potential reached-0.443 V vs.Ag/Ag Cl.Therefore,CoP modification can accelerate the transfer of holes at the interface,prolong the life of photogenerated electrons,and promote the enrichment of photogenerated electrons on the 304 stainless steel side,effectively avoiding the loss of metal dissolution.3.CoFe Prussian blue analogue（CoFe-PB）is immobilized on the surface of BiVO₄ by continuous dipping method to obtain BiVO₄/CoFe-PB photoanode material.The photoanode material can effectively protect 304 stainless steel under simulated solar radiation,with an attenuation of only 0.5%within 10 hours,and the system does not need to add a hole sacrificial agent,achieving complete green protection of the metal.Mechanism studies have shown that the CoFe-PB promoter acts as a hole storage layer and can effectively extract the photo-generated holes on the surface of the BiVO₄ photoelectrode,making the BiVO₄/CoFe-PB photoanode store 1-2 times more holes than the BiVO₄ photoanode.The photovoltage of the BiVO₄/CoFe-PB photoanode was 419.6 m V,while the photovoltage of BiVO₄ was 171.7 m V,indicating that the CoFe-PB coating layer also acts as a catalyst to accelerate the water oxidation kinetics at the electrode/electrolyte interface and reduce the photogenerated electrons/holes.The recombination rate suppresses the recombination of electrons and holes and enhances the protection ability of the photocathode.