Direct growth of WS₂ nanosheets using RF-magnetron sputtering on hydrothermally grown TiO₂ nanorods for enhancing photoelectrochemical water splitting

Using a two-step process to enhance photoelectrochemical (PEC) water splitting for hydrogen production, WS₂/TiO₂ (WT) heterostructures were fabricated on the FTO substrate. First, TiO₂ nanorods were prepared using the hydrothermal method. Next, WS₂ nanosheets were deposited onto the TiO₂ nanorods using RF-magnetron sputtering with different WS₂ deposition times. Herein, investigations were presented regarding the impact of WS₂ deposition time on the structural, optical, morphological, and PEC characteristics of WT heterostructures. The formation of pristine TiO₂ and WT heterostructures was confirmed by low-angle x-ray diffraction, Raman spectra, and x-ray photoelectron spectroscopy. The reduced charge carrier recombination is verified by PL analysis. PEC activities of synthesized pristine TiO₂ nanorods and WT heterostructures were investigated by chronoamperometry, linear sweep voltammetry, electrochemical impedance spectroscopy, and Mott-Schottky (M − S) analysis. We observed that the PEC activities of WT heterostructure photoanodes are directly affected by the deposition time of WS₂. The positive slope of the M − S plots demonstrates the n-type semiconducting nature of WS₂ and TiO₂ nanorods. The WT heterostructure having a WS₂ deposition time of 30 min (WT-30) exhibits the utmost PEC activity, with the photocurrent density around 2.07 mA/cm² at 0.7 V bias potential almost 3 times greater than pristine TiO₂, when exposed to 100 mW/cm² light. The WT-30 photoanode exhibits the highest applied bias photon to current conversion efficiency of 1.52 %, nearly 3.23 times greater than the pristine TiO₂ photoanode. The improved PEC performance is due to the increased number of active sites for photoelectrochemical reactions and better charge transport achieved by adding WS₂ nanosheets to TiO₂ nanorods. Additionally, the photocurrent remains stable for over ∼4000 s, showing that the WT-30 photoanode is a promising material for hydrogen production.