{202}-Dominated WO₃ Nanosheet Arrays Boosting Hole Transport for Efficient Photoelectrochemical Water Oxidation

Metal oxide photoanodes with exposure of specific facets generally exhibit distinct photoelectrochemical (PEC) performances; however, the critical role of facet-dependent hole transport in determining the overall efficiency remains underexplored. Herein, a high-performance WO₃ photoanode is presented via a seed-mediated epitaxial growth strategy, featuring well-built nanosheet arrays with high percent {202} facets. Comparative studies reveal that a 320% increase of hole mobility along {202} facets relative to {200} ones, serves the trigger of efficient carriers' separation. Owing to this "hole highway" effect, {202}-dominated WO₃ photoanode exhibits significantly enhanced PEC efficiency with excellent stability, delivering a remarkable photocurrent density of 3.87 mA cm^-2 at 1.23 V_RHE under AM 1.5G illumination, which reaches 96.8% of the theoretical maximum for the WO₃ photoanode. First-principles calculation combined with characterizations further manifest the lowered activation energy barrier for fast water oxidation kinetics on {202} surface with tetra-coordinated W atomic configuration. Particularly, it promotes the rate-determining step (O^* → OOH^*) in oxygen evolution reactions (OER), and minimizing the accumulation of O^* intermediates. This work proposes a novel design concept for facet-control of semiconductors, and establishes a viable pathway to develop efficiently solar-driven water splitting.