Engineering a Ce Promoter into a Three-Dimensional Porous Mo2C@NC Heterostructure for Hydrogen Evolution Electrocatalysis via Weakening the Mo–H Bond Strength

The pursuit of highly efficient electrocatalysts for the alkaline hydrogen evolution reaction (HER) is of paramount importance for water splitting. However, it is still a formidable task in Mo₂C-based materials because of the agglomeration and strong Mo-H binding of Mo₂C units. Herein, a novel CeOCl-CeO₂/Mo₂C heterostructure nesting within a three-dimensional porous nitrogen-doped carbon matrix has been designed and used for catalyzing HER via simultaneous morphology and heterointerface engineering. As expected, the optimal CeOCl-CeO₂(0.2)/Mo₂C@3DNC exhibits impressive HER activity, with a low overpotential of 156 mV at a current density of 10 mA cm^-2 coupled with a slight Tafel slope of 62.20 mV dec^-1. Introducing a Ce promoter, that is CeOCl and CeO₂, would endow the interface with an internal electric field and electron redistribution between CeOCl-CeO₂ and Mo₂C induced by the heterogeneous work function difference. Moreover, experimental investigation and density functional calculations confirm that the CeOCl-CeO₂/Mo₂C heterointerface can downshift the d-band center of the active Mo center, weakening the strength of the Mo-H coupling. This proposed concept, engineering Ce-based promoters into active entities involved in the heterostructure to modulate intermediate adsorption, offers a great opportunity for the design of superior electrocatalysts for energy conversion.