Hydrogen production via photoelectrochemical (PEC) water splitting is a promising pathway towards a clean energy cycle that addresses the sustainable development goals of fossil fuel reduction in the near future . A PEC device produces hydrogen from pure water with zero carbon emissions employing a solar-powered photoanode and a photocathode for water oxidation and reduction reactions, respectively . Research on photoanodes attracts significant research interest because of their potential in coupling with diversified solar fuel production processes beyond water splitting, including CO 2 and N 2 reductions . A central difficulty for the rational design of efficient photoanodes is the sluggish kinetics of water oxidation, which involves multiple charge transfer pathways .