Sandwiched NiO/β-Mo2C/RGO as Improved Electrocatalyst for Hydrogen Evolution Reaction: Solvothermal-Assisted Self-Assembly and Catalytic Mechanism

Molybdenum carbide is a cost-effective alternative to Pt-group noble metal electrocatalyst for hydrogen evolution reaction (HER), developing a facile strategy to improve the HER activity of molybdenum carbide and understanding the mechanism is of great concern and challenging. Herein, a solvothermal-assisted self-assembly procedure of fabricating sandwiched NiO/beta-Mo2C/RGO nanocomposite catalyst was reported. Electrochemical measurements demonstrate that the catalytic activity and durability of beta-Mo2C can be significantly improved in the sandwiched NiO/beta-Mo2C/RGO. Comparative studies between various catalysts such as beta-Mo2C, NiO/beta-Mo2C, beta-Mo2C/RGO, and NiO/beta-Mo2C/RGO have been performed to explore the mechanism underpinning their different catalytic performance. Our results revealed that hybrid of beta-Mo2C and RGO resulted in significant improvement in electrical conductivity, NiO loading modified the electron density on the surface of beta-Mo2C (101) to the electron-rich state to generate highly active catalytic site. The synergistic effect of RGO and NiO loading would be responsible for the improved electrocatalytic performance of the NiO/beta-Mo2C/RGO catalysts. The strategy developed in this work not only provides a new pathway for improving HER activity of molybdenum carbide but also deepens fundamental understandings on the structure-reactivity of molybdenum carbide-based nanocomposite catalysts with higher HER activity.