Phosphorus-Modified NiFe ₂ O ₄ –TiO ₂ with Defect Engineering for Enhanced Oxygen Evolution Reaction

The rational design of high-performance electrocatalysts is essential for advancing water splitting and minimizing the cell potential. Herein, we report a solvothermal synthesis of NiFe2O4 nanocubes, followed by oxidative pyrolysis of NiFe2O4, TiO2, and triphenylphosphine (TPP) to construct a phosphorus-modified NiFe2O4–TiO2 nanocomposite, P–NiFe2O4–TiO2. Phosphorus incorporation induces lattice distortions, generates abundant oxygen vacancies in both NiFe2O4 and TiO2, and optimizes the electronic configuration of the composite. The combination of structural and electronic changes significantly enhances both the electrical conductivity and the kinetics of charge transfer. Additionally, phosphorus species function as electron acceptors, promoting the creation of high-valent metal species that act as active sites for oxygen evolution reaction (OER). As a result, the P–NiFe2O4–TiO2 catalyst exhibits outstanding OER activity, achieving low overpotentials of 294 and 321 mV at 10 and 50 mA cm–2 in 1 M NaOH. Moreover, a water-splitting cell using this catalyst reached a low cell voltage of 1.583 V at 10 mA cm–2 in 1 M NaOH, showing almost no activity loss after 50 h, thus outperforming IrO2 benchmarks. This study presents a straightforward method that leverages elemental modifications and vacancy engineering to create effective and long-lasting catalysts for oxygen evolution reaction.