Excellent performance of water oxidation at low bias potential achieved by transparent WO3/BiVO4 photoanode integrated with molecular nickel porphyrin

Abstract In attempt to gain a high efficiency of water splitting at 0.6 V (vs. RHE) with a photoanode for the dual illuminated tandem device design, an ultra-thin transparent WO 3 /BiVO 4 composite photoanode was prepared by spin-coating technology. Incorporation of molecular nickel porphyrin as water oxidation catalyst into the prepared WO 3 /BiVO 4 photoanode greatly promoted the efficiency of hole injection ( η ox ) into the electrolyte. A photocurrent density of 0.26 mA cm −2 was achieved by the hybrid photoanode at 0.6 V (vs. RHE), corresponding to the value of η ox to be 45%. The stability of nickel porphyrin on the WO 3 /BiVO 4 photoanode was investigated by photolysis at 0.82 V (vs. RHE), where the maximum applied bias photon-to-current efficiency for the WO 3 /BiVO 4 /NiTCPP photoanode was obtained.