Photoelectrochemical reforming of glycerol by Bi2WO6 photoanodes: Role of the electrolyte pH on the H2 evolution efficiency and product selectivity

Photoreforming of biomass derivatives is a promising strategy for the production of green hydrogen and chemicals. Herein, nanocrystalline Bi2WO6 photoanodes were applied for the first time for the conversion of glycerol in different pHs. Different from TiO2 photoanodes, the photocurrent for Bi2WO6 films is relatively independent of the applied potential, which is attributed to the preferential glycerol oxidation in detriment of water oxidation. Impedance measurements reveal that photocurrent is limited by the charge transfer on the Bi2WO6 surface and is partially inhibited by the poor desorption of glycerol oxidation products. At pH 6, photocurrents up to 0.69 mA cm−2 are reached with a faradaic efficiency for H2 evolution of 100% and 41% selectivity for formate production. In acid media, this selectivity increases to 88%, but the photocurrent decreases 50%. In alkaline media, glycerol oxidation is facilitated and photocurrents up to 0.80 mA cm−2 are reached at the cost of poor product selectivity.