On a Two-Dimensional MoS ₂ /Mo ₂ CT _x Hydrogen Evolution Catalyst Obtained by the Topotactic Sulfurization of Mo ₂ CT _x MXene

Herein we topotactically reacted sulphur, S, with Mo ₂ CT _x MXene powders to synthesize Mo ₂ CT _x sheets covered by MoS ₂ nanosheets and tested the resulting material as a hydrogen evolution reaction, HER, electrocatalyst. As a result, a high electrochemical active surface area catalyst was obtained. It allows driving a current density of 10 mA cm ⁻² at a low overpotential of only 150 mV. Stabilization of the water activated complex as well as interfacial charge transfer accompanied by changes in the adsorption energy hydrogen are most likely responsible for the high electrochemical activity. Moreover, no efficiency loss was observed under working conditions during 30 h in a 1 mol l ⁻¹ KOH electrolyte, confirming the remarkable electrochemical stability of this composite catalyst.