Efficient Electrocatalytic Hydrogen Evolution from MoS₂-Functionalized Mo₂N Nanostructures

Molybdenum-based compounds and their composites were investigated as an alternative to Pt for hydrogen evolution reactions. The presence of interfaces and junctions between Mo₂N and MoS₂ grains in the composites were investigated to understand their role in electrochemical processes. Here we found that the electrocatalytic activity of Mo₂N nanostructures was enhanced remarkably by conjugation with few-layer MoS₂ sheets. The electrocatalytic performance of Mo₂N-MoS₂ composites in the hydrogen evolution reaction (HER) was revealed from the high catalytic current density of ∼175 mA cm^-2 (at 400 mV) and good electrochemical stability (more than 18 h) in acidic media. Increasing the amount of MoS₂ in the composite, decreases the HER activity. The mechanism and kinetics of the HER process on the Mo₂N-MoS₂ surface were analyzed using Tafel slopes and charge transfer resistance.