Ultrasonically prepared photocatalyst of W/WO(3) nanoplates with WS(2) nanosheets as 2D material for improving photoelectrochemical water splitting

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 WO(3) with WS(2) nanosheets as a 2D material before calcination (WO(3)/WS(2)-90) and after calcination (WO(3)/WS(2)-450) prepared with sonochemical treatment. The WS(2) 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 WO(3)/WS(2) electrode, the WS(2) nanosheets initially transformed to 2D-WO(3). After depositing the WS(2) nanosheets on the WO(3), the photocurrent density increased substantially. The WO(3)/WS(2)-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 WO(3)/WS(2)-90 before calcination and pure WO(3). Mott-Schottky and electrochemical impedance spectroscopy analyses confirmed the fabrication of the WO(3)/WS(2) photoanode after calcination. The deposition of WS(2) nanosheets onto pure WO(3) 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 WO(3) with WS(2) nanosheets as a 2D material (WO(3)/WS(2)-450) enhanced the incident photon current efficiency (IPCE) by 55%. In addition, the applied-bias photon-to-current conversion efficiency of the WO(3)/WS(2)-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 WO(3)/WS(2)-90 and pure WO(3).