Pressure-dependent growth of RF-sputtered WS2 nanostructures for enhanced hydrogen production via photoelectrochemical water splitting

Abstract

This study investigates the influence of process gas pressure during radio frequency (RF) magnetron sputtering on the growth dynamics and intrinsic properties of tungsten disulphide (WS₂) nanostructures for efficient photoelectrochemical (PEC) water splitting. X-ray diffraction analysis reveals that increasing process pressure shifts the preferred orientation of WS₂ crystallites from (002) to (100) while maintaining a consistent crystallite size. Scanning electron microscopy investigation verifies that the film morphology transitions from a more planar structure to a vertically aligned configuration. From the optical analysis, the band gap varies from 1.16 eV to 1.45 eV as the working gas pressure changes. This pressure-dependent growth significantly impacts the electrical and PEC properties of WS₂. At a process pressure of 4 Pa, the highest photocurrent density of ∼ 4.35 mA/cm² is achieved. The lowest depletion width (0.90 nm) and highest carrier concentration (6.80 × 10²⁰ cm⁻³) further justifies the potential ability of WS₂ thin film for enhanced PEC activities. These findings, coupled with a favorable negative shift in the flat band potential, indicate optimized charge carrier transport and enhanced PEC water splitting. Our results provide valuable insights into the growth and optimization of WS₂ nanostructures for efficient hydrogen production via PEC water splitting.