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