Hydrogen evolution mediated by sulfur vacancies and substitutional Mn in few-layered molybdenum disulfide

MoS2 is widely praised as a promising replacement for Pt as electrocatalyst for the hydrogen evolution reaction (HER), but even today, it still suffers from low performance. This issue is tackled by using Mn3+ as surface modifier to trigger sulphur vacancy formation and enhance electron transport in few-layered 2H MoS2. Only 10 at% of Mn is sufficient to transform the semiconductive MoS2 into an active HER electrocatalyst. The insertion of Mn reduces both HER onset potential and Tafel slope which allows to reach -100 mA cm-2 at an overpotential of 206 mV, ten times larger of what undoped MoS2 can achieve. The enhanced activity arises because Mn3+ introduces electronic states near the conduction band, promote sulphur vacancies, and increases the hydrogen adsorption. In addition to its facile production and extended shelf-life, Mn-MoS2 exhibit an efficiency of 73% at 800 mA cm-2@2.0 V when used in proton exchange membrane water electrolysers.