Electrochemical versus Photoelectrochemical Water Oxidation Kinetics on Bismuth Vanadate (Photo)anodes

Abstract

This study reports a comparison of the kinetics of electrochemical (EC) versus photoelectrochemical (PEC) water oxidation on bismuth vanadate (BiVO 4 ) photoanodes. Plots of current density versus surface hole density, determined from operando optical absorption analyses under EC and PEC conditions, are found to be indistinguishable. We thus conclude that EC water oxidation is driven by the Zener effect tunneling electrons from the valence to conduction band under strong bias, with the kinetics of both EC and PEC water oxidation being determined by the density of accumulated surface valence band holes. We further demonstrate that our combined optical absorption/current density analyses enable an operando quantification of the BiVO 4 photovoltage as a function of light intensity.

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

“…Our theoretical findings highlight further the importance of in situ characterization techniques for capturing the electronic structure of photocatalysts in operating conditions. 90 For example, Li et al 91 recently found that BiVO 4 photoanodes showed different flat band potentials and magnitudes of surface band bending under electrochemical and photoelectrochemical water oxidation conditions, resulting in differences in hole generation mechanisms.…”

Origin of the Improved Photoelectrochemical and Photocatalytic Activity in a ZnO-TiO2 Nanohybrid Revealed by Experimental and Density Functional Theory Studies

“…The current energy demand around the globe has intensified the research for clean and renewable energy technologies that can directly abate the continuous deterioration of the environment by achieving zero CO 2 emissions. − In this context, the utilization of solar energy for photocatalysis and photoelectrochemical (PEC) water splitting has attracted an extensive amount of research interest. − In recent times, scientists have focused on photoactive metal oxides as emerging materials owing to their low cost, facile synthesis, and long-term stability. − In the past few years, there has been an enormous amount of interest in the development of heterojunction-based composite materials, with enhanced photoactivity and redox ability. , It has been reported that the selection of materials for heterojunction formation based on their respective band edge positions is crucial to achieve favorable charge carrier dynamics. , In a typical PEC system, the hydrogen evolution reaction (HER) occurs at the photocathode [H + /H 2 at 0 V vs the reversible hydrogen electrode (RHE)], while the photoanode is responsible for the oxygen evolution reaction (OER, O 2 /H 2 O at 1.23 V vs the RHE) . Both photocatalysis and PEC water splitting involve the generation of electrons and holes under light, followed by their transport to the surface.…”

“…The current energy demand around the globe has intensified the research for clean and renewable energy technologies that can directly abate the continuous deterioration of the environment by achieving zero CO 2 emissions. 1 − 5 In this context, the utilization of solar energy for photocatalysis and photoelectrochemical (PEC) water splitting has attracted an extensive amount of research interest. 6 − 9 In recent times, scientists have focused on photoactive metal oxides as emerging materials owing to their low cost, facile synthesis, and long-term stability.…”