Preparation Of BiVO₄ Composite Photoanode And Its Photoelevtrocatalytic Oxidation Of 5-Hydroxymethylfural

The selective oxidation of biomass 5-hydroxymethylfurfural（HMF）to prepare new platform compounds is a key research area of sustainable energy.Traditional HMF selective oxidation methods are mostly high temperature and high pressure,difficult to separate,and toxic wastes are also generated.The use of photoelectrocatalytic technology for selective oxidation of HMF has the advantages of green and mild,high-efficiency reaction.The thermodynamically more favorable selective oxidation of HMF can replace the oxygen evolution reaction（OER）in photoelectrochemical cell（PEC）,which can achieve the purpose of hydrogen production and generate value-added chemical substances.It is beneficial to improve the overall efficiency of PEC.In the field of photocatalysis,the semiconductor BiVO₄ has become a hot spot in photocatalysis research due to its suitable band gap and energy band position.However,the electron-hole of BiVO₄ is easy to recombine,and the energy conversion efficiency is low.Therefore,it is necessary to modify the surface to improve the photocatalytic performance.This paper simulates the Mn₃O₅Ca clusters in Photosynthetic System II（PSII）in nature,supports Ca Mn O_x hole transport layer on the surface of BiVO₄ semiconductor,and uses BiVO₄/Ca Mn O_x for 2,2,6,6-tetramethylpiperidine-1-oxyl（TEMPO）-mediated HMF oxidation.The Ca Mn O_x hole storage layer improves the electron-hole separation efficiency and enhances the ability to selectively oxidize HMF.When the photocurrent density is 0.1 m A/cm²,the potential required for TEMPO oxidation is only 262 m V vs.RHE.The doping of calcium ions further enhances the accumulation of holes and electron-hole separation on the surface of the photoanode.The conversion rate of HMF reached 98.06%,the yield of FFCA was 84.56%,and the selectivity was 86.23%.The BiVO₄ photoanode was modified with CoPi,a cheap and abundant high-efficiency catalyst,and then Ca²⁺ions were introduced on the basis of CoPi to prepare a BiVO₄/Ca CoPi composite photoanode for TEMPO-mediated selective oxidation of HMF.It is found that the Ca CoPi layer with a longer deposition time inhibited OER,the photocurrent of TEMPO oxidation is about 4 times that of BiVO₄,and the potential required for TEMPO oxidation is reduced by about 550 m V（corresponding to 0.2m A/cm²）.The system can achieve high yield and high selectivity under mild conditions.The conversion rate of HMF can reach more than 99%,and the yield of FDCA can reach about 96.20%.The reaction can be completed in 100 minutes,and the reaction time is greatly shortened.The research results show that solar-driven biomass conversion is a feasible anode reaction,and proves the feasibility of effective biomass upgrade in PEC with surface-supported catalyst-modified composite photoanode.