Solar-driven valorisation of glycerol on BiVO4 photoanodes: effect of co-catalyst and reaction media on reaction selectivity

Abstract

The electrochemical valorization of glycerol, a by-product from biodiesel production, has received significant attention, yet systems for the efficient reforming of glycerol that are based on non-precious metals have rarely been reported. Here, we introduce tungsten-doped bismuth vanadate (W:BiVO₄) electrodes combined with an atomic-layer-deposited nickel (oxy)hydroxide (NiO_x(OH)_y) co-catalyst, as a promising photoanode material for the photoelectrochemical (PEC) oxidation of glycerol. To reveal trends in the reaction kinetics and selectivities, glycerol oxidation reaction (GOR) was investigated in varying electrolytes and at different applied biases. The photoanode developed in our study provides a rare example of the efficient production of the high value-added products, dihydroxyacetone (DHA), glyceraldehyde (GALD), and glycolaldehyde (GCALD), in the absence of precious metal catalysts. Under optimized conditions, W:BiVO₄ with a NiO_x(OH)_y co-catalyst features oxidation currents and onset potentials for glycerol/water oxidation that are on par with state-of-the-art transition-metal-oxide photoanodes employed for the reforming of organic species, which marks an important step towards affordable solar-driven electrolyzers and direct alcohol fuel cells.