Facile synthetic approach to produce optimized molybdenum carbide catalyst for alkaline HER

Mo 2 C microspheres synthesis by facile, low cost, and scalable solvothermal route is presented using industrial by product cyclooctatetraene as a carbon precursor, recycled into functional materials for green energy. The microspherical Mo 2 C catalyst exhibited reduced overpotentials of only 138 mV with 85 mV dec −1 Tafel slope in 0.5 M KOH and 170 mV with 88 mV dec −1 Tafel slope in 0.5 M H 2 SO 4 . • Facile, low cost, scalable technique for the synthesis of Mo 2 C by a solvothermal route. • Varying the feed ratio of the precursors enabled us to control the valence states of Mo. • We used cyclooctatetraene, an industrial byproduct that can be recycled into functional materials for green energy. • Active Mo 2 C phase with Mo 3+ and Mo 2+ active centers and low charge-transfer resistance were formed. 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 Mo 2 C microspheres by a solvothermal route. Varying the feed ratio of the precursors enabled us to control the valence states of Mo and achieve optimized Mo 2 C phase formation for HER catalysis. Electrodes with the microspherical Mo 2 C 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 Mo 2 C phase with abundance of Mo 3+ /Mo 2+ 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 Mo 2 C-based electrocatalyst for HER and probably other green energy applications.