Interfacial Engineering of MoP₂-NiCoP Heterostructures for Enhanced Alkaline Water Splitting: A Density Functional...

The outstanding alkaline hydrogen evolution reaction (HER) performance of MoP₂-NiCoP heterostructure has been reported. However, the mechanism behind its catalytic activity remains unclear, and the underlying synergistic catalysis has not been revealed at the atomic scale. Based on these research gaps, the theoretical investigation on the MoP₂-NiCoP heterostructure is conducted, revealing that the MoP₂-NiCoP heterostructure exhibits superior HER activity ( $\Delta G_H$  = -0.016 eV) but limited oxygen evolution reaction (OER) performance ( $\Delta G_{\text{OOH}}-\Delta G_O$  = 2.589 eV). Electronic structure analysis demonstrates that interfacial charge redistribution optimizes the adsorption strength of the H* intermediate, significantly lowering the HER energy barrier while restricting the O* → OOH* transition, thus hindering OER processes. Doping strategies (e.g., W, Ta) further enhance HER performance and a linear scaling relationship between the d-band center ( ${\epsilon }_d$ ) and HER activity descriptor ( $\Delta G_H$ ) shows strong correlation (R² = 0.993). This work reveals the origin of the high intrinsic HER activity and the interfacial synergistic mechanism in the MoP₂-NiCoP catalyst, verifying its lack of effective OER activity. It further identifies a novel strategy for directional enhancement of catalytic performance through electronic structure modulation, establishing a theoretical framework for designing bifunctional electrocatalysts on experiments.