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

Abstract

Using a two-step process to enhance photoelectrochemical (PEC) water splitting for hydrogen production, WS 2 /TiO 2 (WT) heterostructures were fabricated on the FTO substrate. First, TiO 2 nanorods were prepared using the hydrothermal method. Next, WS 2 nanosheets were deposited onto the TiO 2 nanorods using RF-magnetron sputtering with different WS 2 deposition times. Herein, investigations were presented regarding the impact of WS 2 deposition time on the structural, optical, morphological, and PEC characteristics of WT heterostructures. The formation of pristine TiO 2 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 TiO 2 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 WS 2 . The positive slope of the M − S plots demonstrates the n-type semiconducting nature of WS 2 and TiO 2 nanorods. The WT heterostructure having a WS 2 deposition time of 30 min (WT-30) exhibits the utmost PEC activity, with the photocurrent density around 2.07 mA/cm 2 at 0.7 V bias potential almost 3 times greater than pristine TiO 2 , when exposed to 100 mW/cm 2 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 TiO 2 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. • Synthesized WS 2 /TiO 2 (WT) heterostructures using hydrothermal and RF-sputtering. • Investigated impact of WS 2 deposition time on heterostructures. • MS plots show n-type semiconducting nature of WT heterostructures. • WT-30 photoanode shows the highest PEC activity with 2.07 mA/cm 2 at 0.7 V. • WT-30 efficiency is 1.52 %, 3.23 times better than pristine TiO 2 .

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