In situ growth of NiCo-MOF and the derived NiCo2O4/NiCo2O4/Ni foam composite with a wire-penetrated-cage hierarchical architecture for an efficient oxygen evolution reaction

Abstract

A NiCo₂O₄/NiCo₂O₄/Ni foam (NCO/NCO/NF) hybrid composite with a wire-penetrated-cage hierarchical structure was synthesized by in situ growth of bimetallic NiCo metal–organic frameworks (NiCo-MOF) on a NiCo layered double hydroxide (NiCo-LDH) nanowire-modified Ni foam (NF) surface and subsequent heat treatment in air. The NCO/NCO/NF hybrid composite shows higher specific surface area and more active sites than its individual components. The wire-penetrated-cage hierarchical structure of NCO/NCO/NF and the synergistic coupling of NCO hollow nanocages (NCO HNCs), NCO nanowires (NCO NWs) and NF provide a fast electron transfer path, improve the conductivity, accelerate the kinetic reaction rate, and enhance the structural stability. When assessed as an electrode for the oxygen evolution reaction (OER), the NCO/NCO/NF hybrid composite exhibits a low overpotential of 310 mV at 10 mA cm⁻² and current density retention of 91% after a 100 h oxidation reaction, which indicates that it has excellent catalytic activity and durability in the electrocatalytic OER.