Dynamic activation of lattice oxygen in medium-entropy CoNiFe-based spinel oxides decorated with in situ formed alloy for efficient oxygen evolution reaction

Abstract

Spinel oxides are promising electrocatalysts for the oxygen evolution reaction (OER) due to their abundant availability and unique dual catalytic sites. However, it is still a big challenge to improve the performance of OER electrocatalysis through dynamic methods. Herein, a novel medium-entropy spinel (CoNiFe)₃O₄ oxide decorated with in situ formed CoNiFe alloy is synthesized via a one-step solution combustion synthesis (SCS) method. The co-doping of octahedral and tetrahedral sites activates the lattice oxygen of the spinel oxides, enabling the OER electrocatalysis of spinel oxides following the lattice oxygen mechanism (LOM) pathway. Additionally, the in situ formed CoNiFe alloy improves the charge transfer ability of the spinel oxides. Benefiting from the activated lattice oxygen and improved charge transfer ability, the CNF@NF electrode achieves a low overpotential of 276 mV at 10 mA cm⁻² and a small Tafel slope of 50.5 mV dec⁻¹. In addition, it shows good stability for OER electrocatalysis in 1 M KOH electrolyte, with retention of about 85.1% of the current density in a 100-h durability test at 1.551 V (vs. RHE). This work provides an effective method to improve the OER electrocatalytic performance of spinel oxides based on dynamic activation of lattice oxygen.