Improved hydrogen evolution efficiency in water splitting with WO₃ thin film via physical vapor deposition

Abstract

WO₃ has successfully been deposited on indium tin oxide (ITO) substrate via physical vapor deposition (PVD) technique, and X-rays diffraction (XRD) confirmed the deposition of a thin layer that is orthorhombic. The XRD and linear sweep voltammetry (LSV) study of the WO₃ thin film confirmed the type of semiconductor and observed it to be an n-type semiconductor. The scanning electron microscopy (SEM) study revealed the uniform and porous morphology of the thin film, and the particle size of WO₃ was measured to be 34 nm without annealing. Fourier transform infrared (FTIR) confirmed the functional group and particle vibration (stretching, compression) the broad band of stretching of WO₃ is monoclinic and observed to be in the range of 3200–3500 cm⁻¹. The W-O-W peak is noted in the range of 400–500 cm⁻¹, while the W-O peak is recorded in the range of 700–900 cm⁻¹, and furthermore, minor peaks were also recorded in the range of 1400–1700 cm⁻¹. UV spectroscopy provided the absorbance of the solar spectrum in the UV and visible range beyond 400-nm range of wavelength. The maximum absorbance was noted in the UV range (320 nm) and gradually decreases with the wavelength. The maximum percentage transmittance was noted at a wavelength in the 500-nm range, which is 88.67%. The band gap of the deposited thin film was also confirmed via the Tauc plot and observed to be 3.26 eV. The Electrochemical impedance spectroscopy (EIS) small curve of WO₃ is evidence of the low impedance and large photocurrent. The maximum photocurrent confirmed from LSV measurement was noted to be 0.51% at 0.8 V, which is quite good for water-splitting applications. The hydrogen generation of the thin film through photoelectrochemical (PEC) water splitting was observed and found to have an average rate of 1743.09 mol g⁻¹ for 6 h.