Structural Design And Kinetic Regulation Of Bismuth Vanadate Anode For Photoelectrochemical Water Oxidation

With the advancement of industrialization,the consumption of traditional fossil fuels has escalated,prompting countries worldwide to look actively for renewable energy sources.Solar energy is the most abundant green renewable energy,and the conversion and utilization of solar energy have been critical tasks for human social development.Photoelectrochemical(PEC)water splitting technology that produces hydrogen from solar energy is drawing dual attention from industry and academia as it expands storage and usage dimensions.In PEC water splitting technology,the anodic water oxidation reaction involves multi-step electron-proton coupled transfer,and its kinetics are relatively slow,causing rate control on the full water-splitting reaction.Therefore,the selection and structural design of the anode material for water oxidation are crucial for the development of PEC hydrogen evolution technology.Among many semiconductor materials,bismuth vanadate(BVO)is considered an ideal anodic material for PEC water splitting due to its visible light-responsive bandgap,the valence band edge that surpasses the water oxidation reaction potential,and its long carrier lifetime.The ’theoretical maximum photocurrent density that BVO can generate is 7.5 mA/cm2.Nonetheless,BVO electrode photocurrent density and its photoconversion efficiency remain low,mainly due to low charge separation efficiency and slow surface water oxidation kinetics.This research proposes promoting charge separation and surface catalysis through doping and surface structural design to enhance the photoelectrocatalytic efficiency of BVO and strengthen its application potential in PEC water splitting technology.Specifically,this paper covers the following two aspects of research:The first study introduced boron as a doping element into the BVO nanocrystalline porous electrode and optimized the three kinetics processes of PEC.Through engineering strategies,the water oxidation activity of BVO was improved,and the PEC efficiency was increased to about 6.2 mA cm-2 under simulated 1-sun illumination(100 mW cm-2,AM 1.5).This work proposed a simple and applicable method for enhancing the PEC performance of various semiconductor electrodes in different PEC applications.The second study proposed a thin carbon-encapsulation construction that built a three-dimensional networked conductive structure to improve the carrier separation and transfer efficiency of BVO and further enhance its PEC performance.The structure achieved a high photocurrent density of 2.33 mA cm-2 at 1.23 VRHE without any catalyst modification and showed improved stability compared to pure BVO electrodes.With the assistance of a catalyst,the current density can reach about 5.912 mA cm-2 under simulated 1-sun illumination(100 MW cm-2,AM 1.5).These studies provide new ideas and methods for improving and optimizing the PEC performance and offer new insights for the development of PEC applications.Overall,the research results of this paper provide an effective solution for optimizing the water oxidation performance of BVO photoanodes and enhance the application value of BVO in PEC water splitting cells.The doping and coating optimization kinetics approach can be extended to other semiconductor photoelectrode materials.