Characterization of Vertically Aligned MoS₂ Thin Film on Mo Electrode for Hydrogen Evolution Catalyst

Abstract

Vertically aligned MoS₂ (V-MoS₂) thin film was investigated to achieve a cost-effective hydrogen evolution reaction (HER) catalyst. As a simple method, the V-MoS₂ film was deposited by partial sulphurisation of RF sputtered Mo film. The residual Mo layer was used as a bottom electrode instead of an expensive conductive substrate such as a glassy carbon. Different thicknesses of V-MoS₂ were deposited to investigate an HER catalyst characteristic for the V-MoS₂/Mo structure. The crystallinity of V-MoS₂ was maintained even though the thickness of V-MoS₂ was controlled, and was confirmed by comparing the X-ray diffraction, Raman measurement, and estimated exchange current density. As the thickness of V-MoS2 was decreased to 50 nm, the overpotential and Tafel slope were reduced to 0.38 V at 10 mA/cm² and 87 mV/dec, respectively. Based on the theoretical tendency of Tafel slope decline, the estimated optimal V-MoS2 thickness was 40 nm for the V-MoS₂/Mo structure. The fabrication process for V-MoS₂ and the estimated result from the variation of the thickness of V-MoS2 could help to realise a cost-effective HER catalyst using MoS₂.