Incremental Co Enhances Charge Transfer Efficiency and Accelerates Hydrogen Evolution Kinetics in NiCoP

Developing high-performance electrocatalysts for the hydrogen evolution reaction (HER) is crucial for advancing hydrogen production in clean energy systems. In this study, we investigated the role of incremental Co incorporation in nickel-cobalt phosphide (NiCoP) and its influence on the charge transfer efficiency and reaction kinetics of HER. Electrochemical analyses, including Tafel slope measurements and electrochemical impedance spectroscopy (EIS), reveal that incremental Co-based NiCoP with an optimal Co content exhibits a reduced overpotential and faster charge transfer, providing the most pronounced improvements. The XPS results corroborated the experimental findings, indicating that increased Co strengthened the electronic structure interaction among Ni, Co, and P in NiCoP. The availability of Co atoms and the low electronegativity promoted the electron flow to Ni and/or P, accelerated electron migration, and improved HER dynamics. This research demonstrates that adjusting the composition of NiCoP by increasing the incorporation of Co is a practical approach to enhance the catalytic activity and stability in HER applications.