The N, P co-doped carbon-loading Ni3P@Ni heterojunction nanocomposites derived from polybenzimidazoles grafted with oxygen-phosphorus group as high-efficiency electrocatalyst for oxygen evolution reaction

Abstract

Interfacial engineering-induced structural optimization is considered an expectant strategy to elevate the electrochemical activities of earth-abundant electrocatalysts. Herein, the pioneering architecture of Ni₃P@Ni heterojunctions embedded onto N, P co-doped C substrates was effectuated by a combination of the wet-impregnation process of Ni/polybenzimidazoles containing an oxygen-phosphorus group (PBI-OP) precursor and phosphating/carbonization treatment to obtain the Ni₃P@Ni/CNP electrocatalyst. It provides substantial Ni₃P@Ni heterojunction interfacial sites, and the strong interaction between Ni₃P@Ni nanosheets and CNP microspheres promotes the rearrangement of the electronic configuration to modify the electrochemically active sites while enhancing the structural stability and promoting interfacial electron transfer, thus improving the electrocatalytic activity of OER. In addition, the large number of pyridine N species on the electrocatalyst accelerated the diffusion of O₂, further reducing the overpotential of OER. DFT calculation unveiled that Ni₃P@Ni/CNP has a lower activation energy than IrO₂, indicating its extremely positive electrocatalytic effect on the OER kinetics. Ni₃P@Ni/CNP-M exhibits a low overpotential of 239 mV, a low Tafel slope of 52 mV dec⁻¹, and good stability at a current density of 10 mA cm⁻² in 1 M KOH electrolyte. Therefore, interfacial engineering through multi-component structures can provide new inspiration for designing advanced OER electrocatalysts.