Nanostructured bismuth vanadate/tungsten oxide photoanode for chlorine production with hydrogen generation at the dark cathode

Abstract Photoelectrooxidation of chloride ions to chlorine with co-production of hydrogen by water reduction has been proposed as a means of decreasing the net solar hydrogen production cost. So far, however, most such solar-to-chlorine production systems use cost-prohibitive materials and/or show rather small faradaic yield or stability. Here we report the development of earth-abundant, nanostructured bismuth vanadate/tungsten oxide (BiVO 4 /WO 3 ) photoanode assemblies that operate in acidic sodium chloride solution (pH 1; 4 M) to produce chlorine while generating hydrogen at the dark cathode. We show that electrodeposition of 20 nm WO 3 coating protects BiVO 4 from harsh pH and oxidative environments while being catalytically active for chlorine evolution. The heterostructured BiVO 4 /WO 3 photoanodes yield average photocurrent densities of 2.5 ± 0.3 mA cm −2 at 1.42 V RHE (Reversible Hydrogen Electrode) under 1 sun illumination. After two hours of continuous illumination, the best performing devices demonstrate faradaic efficiencies of 85% for chlorine production and ~100% for hydrogen production.