Awakening the Photoelectrochemical Activity of α‐SnWO4 Photoanodes with Extraordinary Crystallinity Induced by Reductive Annealing

Oxide‐based photoelectrodes for solar water splitting have gained growing attention because of their decent stability and cost‐effectiveness. Particularly, α‐SnWO4 has been regarded as a potential next‐generation light absorbing material due to the predicted favorable bandgap of 1.9 eV. Herein, the investigation and amelioration of the crystallinity as a performance dominating factor to the α‐SnWO4‐based photoanode are demonstrated. The improvement is attributed to a unique crystallization process induced by the formation of oxygen vacancies in the reductive atmosphere at 500 °C. The sample exhibits notably enhanced visible‐light absorption and an improved charge transport property. Electrochemical measurements reveal a cathodic shift of the flat‐band potential, corresponding to the impacted band position. The photocurrent is enhanced from 0.03 to 0.42 mA cm−2 (AM1.5, 1.23 VRHE). Such a new treatment can be used as an effective tool for developing α‐SnWO4 into efficient photoelectrocatalytic (PEC) materials. α‐SnWO4 is a novel visible‐light‐absorbing semiconductor with a bandgap of 1.9 eV but suffering from the poor crystallinity. Reductive annealing induces a unique fluidity to its lattice, leading to the desired crystallization. The well‐crystalized material exhibits significantly enhanced photoelectrocatalytic activity. Characterizations indicate that it has stronger light absorption and a better charge transport property than the pristine structure.