Water Oxidation on a CuWO4–WO3 Composite Electrode in the Presence of [Fe(CN)6]3–: Toward Solar Z-Scheme Water Splitting at Zero Bias

Electrodeposited thin films composed of CuWO4–WO3 oxidize water under AM 1.5G irradiation with no electrical bias and simultaneous reduction of [Fe(CN)6]3– at a Pt-mesh auxiliary electrode with a faradaic efficiency of >85%. The quantum efficiency and apparent quantum yield are 7% (at 400 nm) and 0.038%, respectively, in a representative film. Although low, the photoanode is stable, maintaining its steady-state current density (17 μA/cm2) over a 2.5 h illumination period. Through full photoelectrochemical characterization, we identify the specific drawbacks in our material and propose solutions.