In situ synthesis of crystalline Ag–WO3 nanosheets with enhanced solar photo-electrochemical performance for splitting water

Abstract

Monoclinic WO₃ nanosheets preferentially exposing the (100) facet were synthesized successfully by a hydrothermal topological reaction using orthorhombic H₂WO₄ disk particles as the precursor. The evolution mechanism of the morphology and crystal structure transformed into WO₃ nanosheets from H₂WO₄ disk particles has been presented in detail. In this process, the H₂WO₄ disk crystals were firstly split along the direction perpendicular to their b-axis and transformed into thin WO₃ nanosheets through an in situ topological dehydration reaction. Then, the thin nanosheets were dissolved further into smaller WO₃ nanosheets via a dissolution reaction. After the photoreduction reaction between the WO₃ nanosheets and AgNO₃ solution, the mainly exposed (100) facet of WO₃ nanosheets was homogeneously covered by Ag nanoparticles. The photo-electrochemical performance of the obtained WO₃ nanosheets and Ag deposited WO₃ (Ag–WO₃) nanosheets as photocatalysts was evaluated by splitting water using WO₃ monoclinic spherical particles (C-WO₃) as a contrast under simulated sunlight. The results show that the photocurrent density generated by the prepared WO₃ nanosheets is seven times that of C-WO₃, indicating that the (100) facet of monoclinic WO₃ is one of the most photocatalytically active surfaces. In addition, the photocurrent density generated by the prepared Ag–WO₃ sample is 30 μA cm⁻², which is ten times that of the WO₃ sample. The results indicate that the solar light utilization efficiency of the WO₃ sample has been significantly improved after silver deposition on the surface, which implies that it has potential applications in photocatalysis.