Towards activation of amorphous MoSx via Cobalt doping for enhanced electrocatalytic hydrogen evolution reaction

Abstract

Amorphous molybdenum sulfide (a-MoSx) has been shown as one of the most promising catalysts in acidic electrolytes towards hydrogen evolution reaction (HER). Its intrinsic electrocatalytic activity can be further enhanced via doping and cropping the electronic structure.In this study, one-step electro-deposition was employed to fabricate MoSxCoy/TNAs hybrid electrodes using TiO2 nanotube arrays as support. The microstructure and chemical composition of the samples were characterized via X-ray diffraction (XRD), scanning electron microscope (SEM), tunneling electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). The electrochemical properties of the samples were investigated through linear sweep voltammetry (LSV), cyclic voltammetry (CV), Tafel curves, and electrochemical impedance spectroscopy (EIS). According to experimental results, MoSCo structure was formed after Co2+ was incorporated into MoSx, resulting in increases in both unsaturated Mo and S atoms acting as the active sites that lead to enhancement of intrinsic electrocatalytic activity. The pseudo-capacitance of MoSxCoy/TNAs (x = 1.70, y = 0.25) reached 46 mF cm−2, a 31.4% improvement over 35 mF cm−2 of MoSx/TNAs. The onset hydrogen evolution potential, overpotentials at current densities of −10 mA cm−2 and –20 mA cm−2 were recorded at −92 mV, −173 mV, and −209 mV, respectively, reduction of 30 mV, 24 mV, and 28 mV than −112 mV, −197 mV, and −237 mV of MoSx/TNAs, respectively. This electrode was subjected to 1000-cycle testing and demonstrated stable electrochemical activity, illustrating excellent stability.