Cobalt phosphate modified 3D TiO2/BiVO4 composite inverse opals photoanode for enhanced photoelectrochemical water splitting

The search for highly efficient, stable and cost-effective photoanode materials for the photoelectrochemical solar water splitting process has attracted much attention over the past decades. In this work, we synthesized a TiO2 inverse opal composite photoelectrode that was sensitized with BiVO4 as light absorber and was further integrated with a cobalt-phosphate (Co-Pi) co-catalyst to boost the kinetics of surface water oxidation reaction. The prepared TiO2/BiVO4/Co-Pi electrode exhibited both improved visible light absorption and a more efficient charge transfer relay for solar driven water splitting. The optimized TiO2/BiVO4/Co-Pi photoanode yielded a photocurrent density of ∼4.96 mA/cm2 at 0.63 V versus Ag/AgCl, leading to a photo-to-energy conversion efficiency that was 9.0 times better than TiO2 inverse opals and 2.3 times better than the TiO2/BiVO4 photoanode. This current work provides a strategy for the design other integrated photoelecreodes that will combine light absorber and co-catalyst for more efficient photoelectrochemical water splitting applications.