Cation Substitution-Induced Electronic and Defect Regulation in Spinel Cobalt(II,III) Oxides for Acidic Oxygen Evolution Reactions

The high cost and scarcity of noble metal anode catalysts significantly hinder the commercialization of proton exchange membrane (PEM) water electrolyzers. These limitations have inspired the development of non-noble metal oxygen evolution reaction (OER) catalysts with high activity and stability for large-scale green hydrogen production. Herein, we report the synthesis of a Ce-modulated cobalt (II, III) oxide (CeCo 3 O 4 ) OER catalyst via metal–organic framework-assisted electrodeposition and low-temperature annealing. This catalyst enables the construction of three-dimensional (3D) cubic architectures on carbon cloth (CC) via controllable defect chemistry, where Ce incorporation effectively modulates the electronic structure of Co sites by regulating the Co 3+ /Co 2+ ratio and oxygen vacancies, thereby stabilizing the catalyst, even under acidic OER conditions. The resulting optimized 3D-CeCo 3 O 4 //CC catalyst delivers an overpotential of 202 mV at a current density of 10 mA/cm 2 in 0.5 mol/L sulfuric acid and exhibits durable operation with minimal potential drift over 100 h. When implemented as the anode of a practical PEM electrolyzer featuring a Pt/C cathode (1 mg/cm 2 ), the device delivers a current density of 100 mA/cm 2 at 1.788 V, maintaining stable operation at 50 mA/cm 2 for 15 h with a voltage fluctuation. This performance surpasses those of most reported non-noble metal OER catalysts, with an efficiency gap that remains relative to those of previous state-of-the-art noble metal-based systems. These results reveal that Ce-induced electronic modulation and oxygen vacancy engineering synergistically enhance the acidic OER activity and stability of Co 3 O 4 , offering a viable, scalable strategy for developing non-noble metal OER catalysts for practical PEM water electrolyzers.