Efficient hypochlorous acid (HClO) production via photoelectrochemical solar energy conversion using a BiVO4-based photoanode

A BiVO4/WO3/FTO (FTO: fluorine doped tin oxide coated glass) multilayer photoelectrode was found to be suitable for photoelectrochemical oxidative hypochlorous acid (HClO) production from chloride ions (Cl-). HClO was efficiently produced in the electrolyte solution by irradiating the BiVO4/WO3/FTO photoanode with simulated solar light. It was expected that Cl- would be oxidized to chlorine (Cl-2) by the photogenerated holes on the BiVO4, and then converted to HClO via the disproportionation reaction in an aqueous electrolyte solution. For the first 100 s, the current efficiency for HClO production was 97%, indicating that the photogenerated hole oxidized Cl- with high selectivity in preference to H2O. Moreover, the BiVO4/WO3/FTO multilayer photoanode enabled us to achieve significant diminution of the external bias required for HClO production under solar light irradiation.