Heating and P doping promote NiFe₂O₄ to achieve a faster oxygen evolution reaction pathway

The oxygen evolution reaction (OER)is crucial for the development of energy storage technologies such as water splitting for hydrogen production and metal-air batteries; therefore, developing efficient electrocatalysts is key to advancing OER. NiFe₂O₄, as a typical spinel-structured transition metal oxide, features nickel ions Ni 2+ preferentially occupying tetrahedral sites and iron ions Fe 3+ occupying octahedral sites within its crystal lattice. This unique dual-metal site distribution significantly optimizes the adsorption energy of oxygen intermediates through Ni Fe electronic synergy, overcoming the inherent activity limitations of single-metal oxides. Simultaneously, its high electrical conductivity and robust stability in alkaline environments make it an ideal alternative to precious metal catalysts. However, its intrinsic activity remains constrained by the sluggish kinetics of the conventional adsorbate evolution mechanism (AEM) and insufficient exposure of surface active sites. To address this, this study focuses on a breakthrough modification of nickel ferrite NiFe₂O₄: employing a phosphorus doping strategy, the reaction mechanism is successfully transformed from the AEM to the lattice oxygen oxidation mechanism (LOM) during the heating process, with optimization of heating time and temperature parameters. The optimized phosphorus-doped nickel ferrite NFO − P achieves a low overpotential of 229 mV and a Tafel slope of 75.1 mV dec −1 at a current density of 10 mA cm −2 —its performance significantly surpasses that of pristine NiFe₂O₄ and approaches the level of precious metal IrO₂. This work concurrently reveals that phosphorus doping overcomes the activity limitations of the traditional AEM pathway by weakening metal‑oxygen bonds and activating lattice oxygen, thereby providing a reference for “AEM → LOM” mechanism regulation in transition metal oxide catalysts.