Regulating local charges of atomically dispersed Moδ+ sites by nitrogen coordination on cobalt nanosheets to trigger water dissociation for boosted hydrogen evolution in alkaline media

Abstract

Now, Pt-based materials are still the best catalysts for hydrogen evolution reaction (HER). Nevertheless, the scarcity of Pt makes it impossible for the large-scale applications in industry. Although cobalt is taken as an excellent HER catalyst due to its suitable H* binding, its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics. In this work, nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Moδ+ sites on Co nanosheets to trigger water dissociation. Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Moδ+ sites. To realize this speculation, atomically dispersed Moδ+ sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO4. High angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XAS) demonstrate the coordination of N atoms with atomically dispersed Mo atoms, leading to the local charges of atomically dispersed Moδ+ sites in Mo(N)/Co. The measurement from ambient pressure X-ray photoelectron spectroscopy (AP-XPS) reveals that the Moδ+ sites promote the adsorption and activation of water molecule. Therefore, the Mo(N)/Co exhibits an excellent activity, which need only an overpotential of 39 mV to reach the current density of 10 mA cm−2. The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.