Photoelectrocatalytic Oxidation of Polyols to Formic Acid at a High Photocurrent Density via a Multihydroxyl-Binding Strategy

Photoelectrocatalytic (PEC) oxidation of biomass-derived polyols into high-value C1 compounds e.g., formic acid (FA) provided a viable route for the efficient utilization of waste biomass. Nevertheless, its practical implementation is severely limited by low photocurrent density and intricate side reactions. In this work, we recorded a multihydroxyl-binding tactic to promote PEC oxidation of polyols (C3-C6) to produce FA under mild conditions. As a typical demonstration, glycerol (GLY) was successfully oxidized to FA over a borate-modified BiVO4 photoanode, reaching a high photocurrent density of 5.64 mA cm-2, and it also achieved a FA production rate of 610 mmol m-2 h-1 and a selectivity of 85.1%. Experimental and spectroscopic characterizations reveal that B(OH)4- chelates primary hydroxyls, while BiVO4 adsorbs secondary hydroxyl of GLY, promoting selective oxidation to FA. As a demonstration of the concept, we fabricated a solar-powered tandem device for the oxidation of polyol waste fluids coupled with H2 evolution, producing FA with high productivity (2.52 mmol) and H2 productivity (0.24 mL) after a 12 h reaction.