Cobalt-molybdenum carbide@graphitic carbon nanocomposites: Metallic cobalt promotes the electrochemical hydrogen evolution reaction

In this work, a series of metallic cobalt-molybdenum carbide@graphitic carbon (CoMo(x:y)-T@GC) nanocomposites for the electrochemical hydrogen evolution reaction (HER) were synthesized by a sol-gel method. In the as-prepared nanocomposites, β-Mo2C and metallic Co coexisted and were encapsulated by graphitic carbon. The presence of metallic Co effectively enhanced the crystallinity of β-Mo2C, charge transfer efficiency and electrochemical active surface area (ECSA), thus resulting in the improved HER catalytic activities of the CoMo(x:y)-T@GC nanocomposites. The optimized electrocatalyst CoMo(0.5:0.5)-800@GC required the lowest overpotential of ∼165 mV to deliver a current density of 10 mA cm−2 in 0.1 M KOH, which was at the forefront compared with recently reported Mo2C-based electrocatalysts.