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

Abstract

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.

The surface reconstruction induced enhancement of the oxygen evolution reaction on α-SnWO4 (010) based on a density functional theory study

“…S5, ESI†) of bulk α-SnWO 4 are also calculated. The results show that the CBM lies on the point of Y and the VBM on the point between G and Z, which agrees with the previous experimental results, 23–25 indicating that bulk α-SnWO 4 is an indirect bandgap semiconductor with a 1.93 eV bandgap.…”

“…For bulk α-SnWO 4 , the calculated bandgap is 1.93 eV, consistent with the experiment at ∼1.90 eV. 23–25 According to the PAW potentials, the valence electron configurations are 5d 4 6s 2 for W, 5s 2 5p 2 for Sn, and 2s 2 2p 4 for O. We evaluate the kinetic energy cutoff at 500 eV as sufficient for effective convergence of plane-wave expansion.…”

“…Experimentally, α-SnWO 4 is promising for overall photoelectrochemical water-splitting. 11,24,61 To explore its mechanism, we also examined the OER performance of the α-SnWO 4 (010) surface for enhanced water-splitting performance. The O–Sn, O–W, and R–OOSn terminations of α-SnWO 4 (010) are modelled by a 2 × 2 surface unit cell with the top ten layers fully relaxed in all directions (the other layers are fixed).…”

“…Experimentally, a-SnWO 4 is promising for overall photoelectrochemical water-splitting. 11,24,61 To explore its mechanism, we also examined the OER performance of the a-SnWO 9a. The largest free energy difference (3.57 eV) is obtained for the third step, which is the rate-limiting step at the zero external potential.…”

Nail-like α-SnWO4 Array Film with Increased Reactive Facets for Photoelectrochemical Water Splitting

“…Some powders (h-BN/α-SnWO 4 , Ag-NPs/α-SnWO 4 , nest-like α-SnWO 4 ) were also fabricated into film electrodes by drop-casting, but the current density is less than 1 μA/cm 2 . Liu et al annealed the powders in hydrogen, which were loaded on the metal layer (Ti&Sn) by drop-casting, and the formed electrode presented ∼100 μA/cm 2 (1.23 V vs reversible hydrogen electrode (RHE)) in KOH/H 3 BO 3 solution . Kölbach et al used SnO and WO 3 as targets to deposit α-SnWO 4 using a pulsed laser with a photocurrent of ∼100 μA/cm 2 (1.23 V vs RHE) .…”