Copper doping-induced high-valence nickel-iron-based electrocatalyst toward enhanced and durable oxygen evolution reaction

Heteroatom doping in NiFe-based electrocatalyst is one of the effective strategies to improve the performance of oxygen evolution reaction (OER). Herein, a nickel foam-supported, copper-doped, tube-structured, nickel-iron-based OER electrocatalyst is fabricated. This Ni(Cu)Fe/NF electrode achieves excellent OER activity with a low overpotential of 240 mV at 20 mA cm−2. When equipped in an anion exchange membrane water electrolyzer, outstanding stability is also achieved at 400 mA cm−2. The underlying mechanism of Cu doping governing the enhanced OER performance is systematically revealed. It is found that the Cu doping in NiFe species induces the formation of high-valence Ni state and the reconstruction of active γ-NiOOH species. This Cu-doped γ-NiOOH presents strengthened Ni-O bonding, resulting in favorable adsorption energy of active OER intermediates with reduced energy barriers, thus accelerating the catalytic reaction kinetics. The working mechanism of Cu-doped NiFe catalysts is instructive for the rational design of NiFe-based OER catalysts.