Effective Corrosion-Resistant Single-Atom Alloy Catalyst on HfO2-Passivated BiVO4 Photoanode for Durable (~800 h) Solar Water Oxidation: Article No. 2402607

Green hydrogen (H2) production from solar water splitting necessitates photoelectrodes with superior photoelectrochemical (PEC) activity and durability. However, surface defects and photocorrosion instability-especially at high potentials-limit PEC performance and stability. Herein, the prototypical bismuth vanadate (BiVO4) photoanode is used to demonstrate a holistic approach to improve photocurrent density and long-term stability. In this approach, high surface-area nanostructuring of BiVO4 is combined with barium (Ba) doping with semi-crystalline hafnium oxide (HfO2) surface passivation and single-atom nickel platinum (NiPt) catalysts. The introduction of Ba2+ ions into BiVO4 increases the concentration of conductive V4+ ions or the ratio of V4+ ions to oxygen vacancies, avoiding V5+ dissolution during water oxidation. The semi-crystalline HfO2, which serves as a passivation layer, prevents BiVO4 photocorrosion by suppressing harmful chemical reactions when holes are transferred to the electrolyte. The synergistic use of isolated single-atom and Ni-Pt coordination improves charge transfer at the photoanode/electrolyte interface, leading to enhanced PEC kinetics and stability. As a result, a photoelectrode is demonstrated with ~6.5 mA cm-2 at 1.23 V versus a reversible hydrogen electrode (RHE) and continuous operation for 800 h with a negligible degradation rate. This work provides a promising approach to improve photoanodes for PEC H2 production.