Upraising the O 2p Orbital by Integrating Ni with MoO2 for Accelerating Hydrogen Evolution Kinetics

Unique interfacial properties within heterostructures play vital roles in enhancing hydrogen evolution reaction (HER) electrocatalysis. On the basis of the MoO2-Ni heterostructure, we hereby propose an upraised atomic orbital promoted catalytic mechanism for accelerating the HER kinetics. A controllable gradient-pyrolysis approach is adopted on molybdates to integrate Ni with MoO2, possessing numerous phase-separation-induced intimate interfaces. In situ characterizations demonstrate the formation process of MoO2-Ni interfaces and excellent compositional stability under alkaline conditions. The optimized MoO2-Ni catalyst delivers remarkable Pt-like HER activity and good stability with 50 h operation in 1 M KOH. An enhancement of 3 orders of magnitude on the exchange current density is achieved for MoO2-Ni in comparison to the simplex MoO2. Further experimental and theoretical analyses verify the existence of a concentrated surface charge at MoO2-Ni interfaces. Meanwhile, with the incorporation of Ni into MoO2, the most active sites dramatically change from Mo to O atoms at MoO2-Ni interfaces. The Ni contact upraises the O 2p orbital in MoO2, thus strengthening the hydrogen adsorption for enhanced HER kinetics.