Preparation Of A Multi-Element Composite Photoanode Based On Bismuth Vanadate And Its Performance In Photoelectrocatalytic Water Oxidation

The decomposition of water into hydrogen（H₂）and oxygen（O₂）using photoelectrochemical（PEC）technology is a sustainable way to produce chemical fuels.In the past few decades,the development of efficient PEC water decomposition technology has been the goal of people,however,the relatively complex four-electron oxygen generation process is considered to be the main factor limiting the water decomposition reaction rate.Therefore,the development of efficient and cheap photoanode materials is one of the research emphases in the PEC water decomposition.Bismuth vanadate（BiVO₄）photoanode has been widely used in the PEC water decomposition due to its suitable band structure and high stability,but its poor charge mobility and slow surface catalytic kinetics seriously limit its practical application.In this paper,we employ modification of oxygen evolution cocatalyst（OEC）onto the surface of BiVO₄ to achieve efficient water oxidation kinetics.Additionally,we introduce an interlayer of either inorganic or organic matter to regulate its sluggish charge transfer in the photoanode.The specific research is as follows:1.The BiVO₄/Mg O/FeCo₂O₄ composite photoanode was fabricated with bimetallic spinel oxide FeCo₂O₄ as a cocatalyst and Mg O as an interlayer to enhance the efficiency of water splitting through PEC reaction.The Mg O layer effectively prevents hole back transfer,significantly reducing electron-hole（e^--h⁺）recombination.In addition,the BiVO₄/Mg O/FeCo₂O₄ sample was treated with a low-temperature plasma to make it super-hydrophilic,thus providing efficient charge transfer and rich electrolyte/electrode interface contact.The photochemical determination results demonstrate the exceptional photoelectrocatalysis performance of H-BiVO₄/Mg O/FeCo₂O₄ in water oxidation.Under AM 1.5G（100 m W/cm²）light,the photocurrent can reach 4.3 m A/cm²(1.23 V_RHE),which is 5.2 times that of BiVO₄.The maximum photon current conversion efficiency（IPCE）is 61.7%,which is 5.1 and 1.7 times BiVO₄ and BiVO₄/FeCo₂O₄,respectively.In addition,the charge separation efficiency of H-BiVO₄/Mg O/FeCo₂O₄ is also greatly improved,reaching 83.4%.In this paper,an effective and simple strategy is proposed to inhibit photogenerated carrier recombination in the plane or between layers.2.The BiVO₄/TAPT/NiFe-LDH photoanode was prepared by layer-by-layer deposition which incorporates 2,4,6-tri（4-aminophenyl）-1,3,5-triazine（TAPT）as an interlayer with a donor-π-A（D-π-A）structure and layered dihydroxides NiFe-LDH as a cocatalyst.The electrode exhibits a current density of 5.0 m A/cm² at 1.23 V_RHE,which is3.3 times higher than that of BiVO₄ and achieves a maximum ABPE value of 1.8%(0.66V_RHE)under biased voltage conditions.In addition,the BiVO₄/TAPT/NiFe-LDH photoanode maintained an initial photocurrent density of about 80%after a 3 h PEC water decomposition test,and the Faraday efficiency was about 97.2%.BiVO₄/TAPT/NiFe-LDH composite photoanode has the advantages of excellent photoelectrocatalysis water oxidation performance and easy layer-by-layer synthesis.This new design strategy is expected to be implemented in the promising field of PEC water splitting for future applications.3.A composite photoanode of BiVO₄/TAPT/NiCo₂O₄ was successfully fabricated,utilizing TAPT as an interlayer and bimetallic spinel oxide NiCo₂O₄ as a cocatalyst,building upon the preceding chapter.BiVO₄/TAPT/NiCo₂O₄ not only obtained a photocurrent density of 4.7 m A/cm² at 1.23 V_RHE,but also achieved a separation efficiency of 89.4%,and the maximum ABPE value at 0.67 V_RHE was 1.6%,about 8 times that of BiVO₄.Through the analysis of the photoelectric chemical test results,it can be found that the higher photoelectrocatalysis performance may be attributed to the fact that TAPT,as the hole transport layer,can effectively promote the transfer of holes,thus accelerating the dynamic process of water decomposition.This not only proves the general suitability of TAPT as an interlayer for water decomposition in PEC but also provides a reference for rational design and manufacture of photoanode for solar energy conversion.The experimental results indicate that the incorporation of oxides and small organic molecules as an interlayer between BiVO₄/OEC has significant potential for practical application in PEC water splitting,while also providing valuable reference for future design and preparation of photoanode materials.