Engineering the Near-Surface Structure of WO 3 by an Amorphous Layer with Trivalent Ni and Self-Adapting Oxygen Vacancies for Efficient Photocatalytic and Photoelectrochemical Acidic Oxygen Evolution Reaction.

Exploiting an effective strategy to tailor the construction, composition, and local electronic structure of the photocatalyst surface is pivotal to photocatalytic activity, but remains challenging. Transition metal elements can boost the oxygen evolution reaction activity especially one like Ni in high oxidation states, whereas it is uneasy to prepare Ni under mild conditions or play to their strengths in acidic conditions. In this article, we report a facile "etch and dope" synthesis of Ni-doped WO nanosheets with oxygen vacancies. Through detailed experimental and theoretical studies, it is established that the abundant oxygen vacancies and the doped Ni ions in the near-surface amorphous layer can synergistically optimize the surface electronic structure of WO and the adsorption and desorption of intermediates. Impressively, the etched WO nanosheets coupled with Ni offer a greatly promoted photocatalytic performance of 1.78 mmol g h, and the photoanode achieves a photocurrent density of 2.11 mA cm at 1.23 V versus reversible hydrogen electrode (V). This work provides a new inspiration for rational manufacture of defects and high-valence metal ions in catalysts for photocatalytic and photoelectrochemical reactions.