Threshold carbonization exceptionally upgrading intrinsic activity of molybdenum carbide for alkaline hydrogen evolution

Developing high-activity non-noble metal catalyst to replace high-cost Pt-based catalyst to catalyze hydrogen evolution reaction (HER) is desirable but challenging for industry-level hydrogen production from water splitting. Molybdenum carbide (Mo 2 C) possesses Pt-like d -band structure, however, its HER performance is far away from that of Pt-based catalyst. In this work, a threshold carbonization strategy is developed to substantially upgrade the intrinsic activity of Mo 2 C catalyst for electrochemical HER. The prepared Mo 2 C-700 catalyst exhibits overpotential of as low as 90 mV for achieving current density of 10 mA/cm 2 in alkaline electrolyte and excellent catalytic durability, being close to Pt-based catalyst and outperforming most reported Mo 2 C-based catalysts. Mechanism studies demonstrate that threshold carbonization reaction of MoO 3 with H 2 /CH 4 at 700 °C substantially inhibits the formation of carbon deposits and leads to more exposed Mo sites and hydroxyl groups on the surface of Mo 2 C-700 catalyst, thus endowing the Mo 2 C-700 catalyst with superhydrophilic and superaerophobic surface to facilitate water adsorption and H 2 bubbles release. Density functional theory calculations reveal that the less carbon deposits on Mo 2 C catalyst surface upgrades the Mo d -band center toward Fermi level, substantially enhances the capacity of water adsorption, decreases the energy barrier of water dissociation reaction, and furthermore, results in near-zero hydrogen adsorption Gibbs free energies on Mo 2 C catalyst, thus endowing Mo 2 C-700 exceptional activity for alkaline HER.