M (M = Co, Zn)-modified Ni2P with carbon coating grown on Ni foam as efficient electrocatalysts for overall water splitting under fluctuating power

Electrolyzing water to produce hydrogen is currently one of the most attractive methods to alleviate the energy problem and environmental pollution. However, the slow oxygen production kinetics and complex mechanism have greatly limited its large-scale application. In our study, multiple types carbon-encapsulated C@M-Ni 2 P/NF (M = Co, Zn) were synthesized via impregnation and phosphidation process for the first time to address the need for environmentally friendly and high-performance bifunctional catalysts in electrocatalytic water splitting. Electrochemical tests revealed C@Co-Ni 2 P/NF present excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activity in an alkaline medium. The overpotentials were 196/255/294 mV at 10/50/100 mA·cm −2 (Tafel slope 34.20 mV·dec −1 ) for OER; the overpotentials were 199/311/363 mV for HER, which is outperforming C@Zn-Ni 2 P/NF, Ni 2 P/NF, and bare NF. The experimental analysis demonstrate that the improvement in performance for C@Co-Ni 2 P/NF is attributed to a “crack-texture interwoven” hierarchical pore structure and a protective surface carbon layer. In addition, when it is assembled into a two-electrode system, the electrolytic cell demonstrates excellent electrochemistry performance and acceptable durability under fluctuating power. In-situ Raman characterization demonstrated that the in-situ generated NiOOH and CoOOH, along with the material itself, synergistically catalyzed, resulting in the high activity of the catalyst. Density functional theory (DFT) analysis confirmed Co modification optimized water adsorption energy (-0.52 eV) and enhanced conductivity of C@Co-Ni 2 P/NF electrode by regulation of the d -band center. This study offers a promising and feasible strategy for developing robust and high-performance electrocatalysts.