Crystalline-Amorphous Interfaces Coupling of CoSe 2 /CoP with Optimized d-Band Center and Boosted Electrocatalytic Hydrogen Evolution.

Amorphous and heterojunction materials have been widely used in the field of electrocatalytic hydrogen evolution due to their unique physicochemical properties. However, the current used individual strategy still has limited effects. Hence efficient tailoring tactics with synergistic effect are highly desired. Herein, the authors have realized the deep optimization of catalytic activity by a constructing crystalline-amorphous CoSe 2 /CoP heterojunction. Benefiting from the strong electronic coupling at the interfaces, the d-band center of the material moves further down compared to its crystalline-crystalline counterpart, optimizing the valence state and the H adsorption of Co and lowering the kinetic barrier of hydrogen evolution reaction (HER). The heterojunction shows an overpotential of 65 mV to drive a current density of 10 mA cm -2 in the acidic medium. Besides, it also shows competitive properties in both neutral and basic media. This work provides inspiration for optimizing the catalytic activity through combining a crystalline and amorphous heterojunction, which can be implemented for other transition metal compound electrocatalysts.