Solution Synthesis of Defect-Minimized and Visible-Light-Active Tin Tungstate (α-SnWO₄) Nanosheets for Enhanced Photocatalytic and Photoelectrochemical Activities

The photocatalytic and photoelectrochemical (PEC) performances of semiconductor materials strongly depend on their morphology and structural properties. Here, α-SnWO4 (SWO) nanosheets with high crystallinity and reduced oxygen vacancy were successfully synthesized via a simple solvothermal approach using an ethanol–water solvent mixture. The formation mechanism of α-SnWO4 nanosheets involves dissolution-recrystallization coupled with oriented attachment, as confirmed by systematic scanning electron microscopy and X-ray diffraction analyses. Transmission electron microscopy analysis revealed that the nanosheets exhibited a layered orthorhombic crystal structure with high crystallinity, even at the edge. Compared with bulk SWO (2.8 m2/g), the nanosheets exhibited a substantially increased specific surface area (63.7 m2/g), significantly enhancing their visible-light absorption capability. Consequently, the α-SnWO4 nanosheets demonstrated superior photocatalytic degradation of rhodamine B under visible-light irradiation (>420 nm) and substantially enhanced PEC water oxidation performance compared with their bulk counterparts. This study provides insights into morphology-controlled synthesis and highlights the promise of α-SnWO4 nanosheets as efficient visible-light-driven catalysts for environmental remediation and solar-energy conversion.