{202}‐Dominated WO 3 Nanosheet Arrays Boosting Hole Transport for Efficient Photoelectrochemical Water Oxidation

Abstract 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 WO 3 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 WO 3 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 WO 3 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.