Awakening the photoelectrochemical activity of α-SnWO${}_4$ 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-SnWO${}_4$ 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-SnWO${}_4$-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${}^{-2}$ (AM 1.5, 1.23 V${}_{RHE}$). Such a new treatment can be used as an effective tool for developing α-SnWO${}_4$ into efficient photoelectrocatalytic (PEC) materials. (© 2021 The Authors. Advanced Energy and Sustainability Research published by Wiley‐VCH GmbH)