An in situ formed ZIF-67 derived NiFeCo-P nano-array for accelerating the electrocatalytic oxygen evolution reaction

Abstract

In situ growth of nano-arrays on substrate materials is a neoteric and efficacious catalyst design strategy, but it is still a difficulty to prepare unique nano-structured electrocatalysts with excellent activity for the oxygen evolution reaction (OER). In this study, phosphidizating ternary nickel/iron/cobalt hybrid nano-arrays (NiFeCo-P) with vertically staggered growth were successfully synthesized on the surface of nickel foam (NF) through three steps: impregnation, hydrothermal reaction and phosphidizating calcination. The initial ZIF-67/NF and the derived NiFeCo-layered double hydroxide (LDH)/NF nano-array (NiFeCo-LDH/NF) template promote the charge transfer and ion diffusion between electrolyte surfaces, which is attributed to the enhancement of the interface contact area of electrolyte ions. Phosphidizated NiFeCo-LDH/NF nano-arrays (NiFeCo-P/NF) showed lower overpotential of 251 and 278 mV at 50 mA cm⁻² and 100 mA cm⁻², respectively. The Tafel slope was 25.24 mV dec⁻¹, which was better than the performance of some transition metal-based OER catalysts reported before. Electrochemical impedance spectroscopy further revealed the good kinetics in the electrolysis process. Furthermore, the high structural stability of the nanosheet array promotes the generation of the active phase in the OER process, so it has good stability after continuous operation for 20 h at a current density of 50 mA cm⁻².