Enhanced Photoelectrochemical Activity Realized from WS2 Thin Films Prepared by RF‐Magnetron Sputtering for Water Splitting

Abstract We report the synthesis of tungsten sulfide (WS 2 ) films using RF‐magnetron sputtering at different RF powers. X‐ray diffraction (XRD) data confirm the hexagonal crystal structure of WS 2 with an average crystallite size of ∼44.54 Å. With increased RF power, the preferred orientation of WS 2 crystallites shifts from (002) to (100). Linear sweep voltammetry (LSV) was used to assess the Photoelectrochemical (PEC) activity of WS 2 films. The film deposited at 150 W demonstrated the highest photocurrent density of 5.44 mA/cm 2 . The 150 W film also showed a lower Tafel slope of ∼0.374 V/decade, indicating superior PEC activity. Mott Schottky's (MS) analysis revealed a notable shift in the flat band potential towards the negative side, suggesting a shifting of the Fermi level towards the conduction band. WS 2 film grown at 150 W demonstrated a majority charge carrier density of 6.2×10 21 cm −3 and a depletion layer width of 1.54 nm. The observed low charge transfer resistance of 155 Ω contributed to the enhanced PEC activity with a relaxation time constant of 37 ms. These properties suggest that WS 2 can be suitable for PEC water splitting.