Derived Carbon–Nitrogen Codoped Co ₃ O ₄ with Abundant Crystalline Defects for Enhanced Electrocatalytic Oxygen Evolution

A major bottleneck in electrocatalytic water splitting for hydrogen production lies in the slow kinetics of the anodic oxygen evolution reaction (OER). The rational design of electrocatalysts aimed at optimizing the anodic overpotential and operational stability is essential. Herein, we report a C,N-codoped Co 3 O 4 electrocatalyst (CoPc-375) obtained via a one-step thermal oxidation of cobalt phthalocyanine (CoPc) as the sole precursor. The effects of C,N doping on the crystal structure and electronic properties of Co 3 O 4 were systematically investigated. Comprehensive characterization results revealed that controlled C,N doping induced lattice distortion in Co 3 O 4, significantly increasing the internal crystalline defect density of the catalyst. Simultaneously, strong residual carbon–cobalt interfacial interactions modulate the electronic structure and decrease the cobalt valence state, which in turn unlocks the intrinsic catalytic activity of Co 3 O 4 . Electrochemical tests demonstrated that the optimized CoPc-375 exhibits exceptional OER activity and long-term stability in 1.0 M KOH electrolytes: a low overpotential of 282 mV@10 mA cm –2, high mass activity of 87.36 A g –1, and maintaining stable operation for 25 h even at a high current density of 100 mA cm –2 . This work provides a universal, scalable strategy for enhancing the electrocatalytic performance of metal oxide-based catalysts, offering valuable insights for the development of efficient electrocatalysts.