Modulating Surface Oxygen Valence States via Interfacial Potential in BiVO4/CoOx/Au Photoanode for Enhanced Selective Photoelectrochemical Oxidation of Glycerol to Dihydroxyacetone

Abstract

The concept of photoelectrochemical conversion of biomass into industrially valuable chemicals presents a compelling strategy to supplant the lower-value oxygen evolution typically associated with photoanodes. Here, a surface potential manipulation method by regulating the surface oxygen valence states is put forward, which is demonstrated to be effective in enhancing the selective photoelectrochemical oxidation of glycerol to dihydroxyacetone (DHA). This involves the concurrent establishment of a BiVO₄/CoO_x heterojunction and a BiVO₄/Au Schottky junction, aiming to fine-tune the BiVO₄ photoanode's surface potential and improve both its charge carrier separation and interfacial transfer kinetics. The BiVO₄/CoO_x/Au photoanode exhibits a photocurrent density of 6.15 mA cm⁻² at 1.23 V versus reversible hydrogen electrode (RHE). Meanwhile, selective glycerol oxidation efficiency achieves a DHA evolution rate of 339.74 mmol m⁻² h⁻¹ and a selectivity exceeding 60%. Experiments and theoretical analysis underscore the pivotal role played by the surface potential in mediating glycerol and DHA adsorption and desorption processes. Additionally, the diminished surface potential attributed to the CoO_x and Au amendments is responsible for the decreased Gibbs free energy of the dehydrogenation's rate-limiting step involving the intermediate carbon species. This work demonstrates a method to design glycerol oxidation catalysts by modulating the interfacial molecular adsorption/desorption by surface potential regulation.