Ultrasonically prepared photocatalyst of W/WO3 nanoplates with WS2 nanosheets as 2D material for improving photoelectrochemical water splitting

Abstract

A sonochemical treatment has been an emerged technique as an interesting method for fabricating different photocatalysts with unique photoelectrochemical (PEC) properties. This study investigated the PEC performance of WO3 with WS2 nanosheets as a 2D material before calcination (WO3/WS2-90) and after calcination (WO3/WS2-450) prepared with sonochemical treatment. The WS2 nanosheets were prepared from a liquid exfoliation phase with few-layer nanosheets, approximately 6.5 nm in thickness. The nanosheets were confirmed by UV–Vis spectroscopy and atomic force microscopy. Further, XPS, RAMAN, and SEM-EDAX analyses indicated that, following calcination of the WO3/WS2 electrode, the WS2 nanosheets initially transformed to 2D-WO3. After depositing the WS2 nanosheets on the WO3, the photocurrent density increased substantially. The WO3/WS2-450 films after calcination showed a photocurrent density of 5.6 mA.cm−2 at 1.23 V vs. Ag/AgCl, which was 3.1 and 7.2 times higher, respectively than those of the WO3/WS2-90 before calcination and pure WO3. Mott-Schottky and electrochemical impedance spectroscopy analyses confirmed the fabrication of the WO3/WS2 photoanode after calcination. The deposition of WS2 nanosheets onto pure WO3 increased the donor concentration (24-fold), reduced the space charge layer (4.6-fold), and decreased the flat band potential (1.6-fold), which could all help improve the photoelectrochemical efficiency. Moreover, the incorporation of WO3 with WS2 nanosheets as a 2D material (WO3/WS2-450) enhanced the incident photon current efficiency (IPCE) by 55%. In addition, the applied-bias photon-to-current conversion efficiency of the WO3/WS2-450 films was approximately 2.26% at 0.75 V (vs. Ag/AgCl), which is 5.6 and 9 times higher, respectively than those of WO3/WS2-90 and pure WO3.