Enhancing Photoelectrochemical Performance of the Printed Nanoporous FeVO₄ Photoanode by Dual-Layer CoO _x -CoPi Catalysts

Photoelectrochemical solar water splitting has becomea potentialapproach for producing clean hydrogen fuels by utilizing semiconductorphotoelectrodes and solar energy. Among emerging metal oxide photoelectrodes,iron vanadate (FeVO4) with its unique electronic band structureand suitable bandgap energies for absorbing visible light from thesolar spectrum has become a promising photoanode. However, the reportedphotocurrent density of this material is still low because of thepoor water oxidation kinetics and the slow separation of carriers,leading to recombination at the surface. In this study, we attemptedto solve these limitations by nanostructuring the FeVO4 photoanode and modifying its surface with cocatalysts (CoO x , CoPi, and CoO x -CoPi).Both photocurrent and onset potential are significantly improved,resulting from the enhancement of charge injection and separationefficiencies. For the first time, the dual layer of oxygen evolutionCoO( x )-CoPi catalysts is found moreeffective than single-layer CoO x or CoPicatalysts for the nanoporous FeVO4 photoanode with theincreased photocurrent density at 1.23 V vs RHE of a 5-fold improvementcompared to the pristine FeVO4. This result offers a strategyto further improve FeVO4 photoanode performance for efficientsolar water splitting toward practical applications.