Regulating surface wettability and electronic state of molybdenum carbide for improved hydrogen evolution reaction

Molybdenum carbide (Mo2C) is a cost-effective transition metal carbides (TMCs) electrocatalyst for hydrogen evolution reaction (HER) due to its electronic structure similar to Pt-group noble metal. Herein, we report that an effective strategy of regulating the surface wettability and electronic state of Mo2C by ammonia and hydrothermal co-treatment to enhance its HER activity. The electrochemical results demonstrate that Mo2C undergoing ammonia and hydrothermal co-treatment (Mo2C-wh) exhibits remarkably improved electrocatalytic HER activity as compared to the pristine Mo2C (Mo2C-p) catalyst. The activity-structure relationship studies manifest that ammonia and hydrothermal co-treatment increases the content of hydroxyl group and pyridinic-N, thus endowing Mo2C-wh with lower charge transfer resistance, larger electrochemical active surface area and higher surface wettability. DFT calculations reveal that ammonia and hydrothermal co-treatment enhances the Mo 3d-band center and reduces the hydrogen adsorption free energy. These changes in electronic states of Mo sites and physical properties of Mo2C positively contribute to the improvement of electrocatalytic HER activity.