One-step synthesis of Cr-doped CoFe2O4 as a kinetically enhanced electrocatalyst for efficient overall water splitting

• One-step hydrothermal synthesis of hierarchical Cr–CoFe 2 O 4 /NF with rich active sites. • Cr promotes low-potential CoOOH formation and improves stability. • AEM electrolyzer reaches 1.0 A cm -2 at 1.76 V for >100 h stability. Developing bifunctional, precious metal-free electrocatalysts capable of efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at high current densities is essential for sustainable industrial hydrogen production via anion exchange membrane water electrolysis (AEMWE). Here, we report a Cr-doped CoFe 2 O 4 catalyst on nickel foam (Cr x /CoFe 2 O 4 /NF) synthesized via a simple one-step hydrothermal method. Cr doping not only optimizes the electronic structure but also increases active site density and accelerates reaction kinetics, resulting in outstanding bifunctional performance. The Cr x /CoFe 2 O 4 /NF electrode achieves an OER overpotential of 307 mV at 300 mA cm −2 and a HER overpotential of 79 mV at − 10 mA cm −2 . When applied as both anode and cathode in an AEMWE electrolyzer, it delivers a low cell voltage of 1.76 V at 1.0 A cm −2 and maintains excellent durability with a degradation rate of only 0.8 mV h −1 over 100 h. Density functional theory (DFT) calculations reveal that Cr doping upshifts the d-band center, weakens Co–O covalency, optimizes oxygen intermediate adsorption, and lowers the energy barrier of the rate-determining step, explaining the enhanced activity and stability. This work provides a facile and effective strategy to design low-cost, noble metal-free electrocatalysts for high-performance, industrially relevant water splitting.