LAUSR

Abstract Mo-based materials were recognized as cost-effective electrocatalysts for the hydrogen evolution reaction (HER) in acidic media but were hardly investigated in alkaline media due to the limited active sites, lower conductivity and high water dissociation energy barrier. Herein, a facile, low cost, scalable technique is provided for the synthesis of Mo2C microspheres by a solvothermal route. Varying the feed ratio of the precursors enabled us to control the valence states of Mo and achieve optimized Mo2C phase formation for HER catalysis. Electrodes with the microspherical Mo2C catalyst were stable and exhibited reduced overpotentials of 138 mV at 10 mA cm-2 in 0.5 M KOH with a Tafel slope of 85 mV dec-1. The formation of an active Mo2C phase with abundance of Mo3+/Mo2+ active sites in the suitable ratio, as well as fast charge-transfer kinetics, are proposed as the origin for the efficient HER activity. Notably, we used cyclooctatetraene, an industrial byproduct that can be recycled into functional materials for green energy. Our work provides facile and novel way to design and fabricate Mo2C-based electrocatalyst for HER and probably other green energy applications.