A Co–Mo2N composite on a nitrogen-doped carbon matrix with hydrogen evolution activity comparable to that of Pt/C in alkaline media

Abstract

Intrinsic activity and electrical conductivity play key roles in the hydrogen evolution reaction (HER). We herein design and synthesise nanocomposites of metallic cobalt and molybdenum nitride on a nitrogen-doped carbon matrix (Co–Mo₂N@NC). The electrocatalyst exhibits extraordinary HER performance with an overpotential of only 47 mV at a current density of 10 mA cm⁻² and Tafel slope of 43 mV dec⁻¹ in a 1 M KOH solution, which is comparable to that of commercial 20 wt% Pt/C (43 mV at 10 mA cm⁻²). At high current density it even exhibits better performance than Pt/C (170 mV vs. 220 mV at 100 mA cm⁻²). The excellent activity stems from the roles of Co nanoparticles in improving electrical conductivity, optimizing the electronic structure and thus speeding up hydrogen desorption from Mo₂N, and of the in situ formed Co(OH)₂ in boosting water dissociation. Therefore, this work provides a low-cost potential electrocatalyst to replace Pt/C.