WO ₃ nanosponge photoanodes with high applied bias photon-to-current efficiency for solar hydrogen and peroxydisulfate production

We prepared WO3 nanosponge photoanodes by nanoparticle/solution hybrid dispersion–deposition. The WO3 nanosponge photoanodes showed a large photocurrent (3.04 mA cm−2) in 1.0 M H2SO4 electrolyte under 1 Sun illumination. This high photocurrent arose from the robust inter-nanoparticle connections and preservation of the nanopores in the photoanode, achieved by the addition of tungsten phenoxide and the very fine nanoparticles obtained by wet milling. The absorbed photon-to-current efficiency spectra showed a high maximum of 95.4% at 410 nm. The Faraday efficiency of S2O82− and H2 evolution was almost 100%, and the applied bias photon-to-current efficiency for S2O82− and H2 was calculated to be 2.45%, which is the highest reported value. Obtaining this kind of high-value-added product efficiently at photoanodes in photoelectrochemical systems is important for the use of sunlight in sustainable industrial chemistry.