Boosting Water Oxidation Performance of Ni Doped BiVO ₄ Photoanodes Functionalized with FeOOH Electrocatalyst

Abstract An important photoelectrocatalyst for solar‐driven hydrogen synthesis is n‐type bismuth vanadate (BiVO 4 ) because of its straddling band alignment with water splitting potentials, visible‐active bandgap (2.4 eV), and outstanding theoretical efficiency. Unfortunately, the actual feasibility of pure BiVO 4 photoanodes is hampered by their restricted hole diffusion length and slow surface oxidation rates. We offer a novel FeOOH@Ni‐doped BiVO 4 photoanode manufacturing method that addresses these issues by dual‐modifying a nanoporous BiVO 4 with bulk nickel doping and a surface iron oxyhydroxide oxygen evolution catalyst (OEC). The solar‐driven water oxidation experiments revealed that the as‐synthesized FeOOH@Ni‐doped BiVO 4 showed a high photocurrent density of 1.62 mA cm −2 at 1.0 V RHE , representing an approximately two‐fold increase with respect to the pristine counterpart. Additionally, the applied bias photon‐to‐current conversion efficiency (ABPE) of the rationally engineered FeOOH@Ni‐doped BiVO 4 photoanode was significantly improved from 0.47% to 0.83%, and the surface charge separation efficiency reached a maximum of 23%. The long‐term photostability studies demonstrated maximum photocurrent retention for 10 h without any significant degradation. We believe our findings open a new avenue for developing a next‐generation photoanode and providing a rational strategy for designing an efficient solar‐assisted water splitting system.