Photoelectrochemical glycerol oxidation to high value-added products over BiVO₄/CuWO₄ heterojunction photoanodes

Developing high-efficiency, long-term stable photoanodes to harness solar energy for photoelectrocatalytic (PEC) glycerol oxidation into value-added chemicals is pivotal for advancing green chemistry. However, controlling selectivity while achieving high efficiency and stability poses a significant challenge in photoelectrode design. Here, a BiVO₄/CuWO₄ (abbreviated as BVO/CWO) heterojunction photoanode was synthesized via an electrodeposition method followed by spin-coating. Under AM 1.5G illumination, the BVO/CWO photoanode achieves a glycerol oxidation current density of 1.55 mA∙cm^-2 at 1.23 V_RHE, maintaining approximately 99 % stability after a 10-hour stability test. The production rate of 1,3-dihydroxyacetone (DHA) for BVO/CWO photoanode reaches 140.3 mmol m^-2 h^-1 at 1.4 V_RHE, representing a nearly 12-fold increase compared to CuWO₄ (12.1 mmol m^-2 h^-1), while the DHA selectivity improves to 50.1 % from 12.5 %. This enhanced performance is attributed to the heterojunction with strong interface interaction within BVO/CWO, which generates a greater photovoltage driving force and improves bulk charge transport efficiency. Introducing the BiVO₄ layer on the CuWO₄ accelerates interfacial reaction rates and inhibits the photo-corrosion of CuWO₄ in strongly acidic conditions. Furthermore, a self-powered system, PEC coupled with a photovoltaic cell (PV-PEC), is developed using a dual-electrode configuration. A PV-PEC device with the BVO/CWO photoanode achieves a DHA productivity of 186.9 mmol m^-2 and an H₂ productivity of 416.4 mmol m^-2 at an operating voltage of 1.5 V over 2.5 h, indicating the application potential of the BVO/CWO photoanode under more realistic conditions.