Boost photoelectrocatalytic selectivity of glycerol to dihydroxyacetone on BiVO4 via accelerating middle hydroxyl oxidation by co-catalysts

Abstract

Enhancing the selective oxidation of glycerol into 1,3-dihydroxyacetone (DHA) on a photoanode is attractive but challenging due to the complex reaction pathway. At present, the 20 % selectivity of DHA products on a BiVO₄ photoanode in neutral condition as well as its photocorrosion prove to be below expectations. In this work, we decorated binary co-catalysts MnO_x/FeOOH on BiVO₄ (denoted BVO/Mn/Fe) for the selective photoelectrocatalytic glycerol to DHA. The BVO/Mn/Fe photoanode exhibited a DHA selectivity of 52 % at 1.2 V_RHE with an evolution rate of 193.3 mmol m^-2h⁻¹ in pH = 7.0, and maintained 97.2 % of the initial photocurrent after 12 h stability test. The role of MnO_x and FeOOH in the selective oxidation of glycerol was investigated through comprehensive spectroscopic and computational methods. Fourier transform infrared spectroscopy showed that the middle hydroxyl group preferentially adsorbs onto MnO_x surfaces, density function theory calculations verified the optimized rate-determining step and decreased energy barrier by MnO_x. Meanwhile, FeOOH significantly increased the active surface states on BiVO₄ and produced more hydroxyl radicals. The synergistic effect of MnO_x and FeOOH promoted the middle hydroxyl oxidation of glycerol and conversion efficiency to DHA on BiVO₄ under neutral condition.