Amorphous MoS electro-synthesized in alkaline electrolyte for superior hydrogen evolution

Recently, amorphous MoSx electrocatalysts have attracted lots of attention because their structural flexibility and rich defects can offer enormous sites for hydrogen evolution. In the deposition solution containing various amount of (NH4)2MoS4 and NaOH, amorphous MoSx films have been electrochemically deposited on carbon cloth by using constant potentials method under ambient conditions. The X-ray diffraction patterns show that the resulted samples are amorphous, X-ray photoelectron and Raman spectrum reveal that amorphous MoSx exists defective MoV=O sites coordinated with bridged sulfur. The electrodepositing conditions have been optimized and the optimal MoSx electrode exhibits overpotential of 156 mV in 0.5 mol L−1 H2SO4 and 232 mV in 1.0 mol L−1 KOH without iR correction for hydrogen evolution reaction (HER) at current density of 10 mA cm−2, which surpasses the property of most of the amorphous MoSx-based electrodes. On the basis of MoV=O as the proposed active sites, the possible catalytic pathway is suggested. More importantly, the optimized MoSx electrode shows excellent stability for HER in acidic and alkaline electrolyte. This approach for synthesis of MoSx in alkaline electrolyte may be developed as effective way to prepare high-performance electrocatalytic electrode for HER.