Transition-Metal Cobalt-Regulated g-C3N4 Composites for Electrocatalytic Oxygen Evolution

Developing efficient and stable non-precious metal catalysts for the oxygen evolution reaction (OER) is crucial for addressing global energy challenges. In this work, unlike conventional powder-based composites that rely on polymeric binders, we engineered a binder-free, three-dimensional (3D) self-supported electrocatalyst by directly incorporating cobalt (Co) and nitrogen-rich graphitic carbon nitride (g-C3N4) onto a nickel foam (NF) substrate. Through a facile in situ calcination approach, a series of nitrogen-containing OER electrocatalysts, denoted as CoCN/NF-x (x = 40–100%), were synthesized. The in situ thermal treatment facilitated the possible Co-N coordination or strong electronic interactions between the nitrogen atoms of the g-C3N4 framework and the Co centers. This unique structural design significantly reduces interfacial contact resistance, prevents active site aggregation, and builds a highly conductive architecture. Electrochemical OER tests revealed that the catalyst with 80% Co content (CoCN/NF-80) exhibited superior electrocatalytic activity. At a current density of 10 mA cm−2, it achieved a low overpotential of 263 mV in 1.0 M KOH. Moreover, it showcased a remarkably small Tafel slope of 61 mV dec−1, indicating highly favorable OER kinetics. After a 12 h chronoamperometric test, the overpotential increased by only 11%, and post-test characterizations confirmed a favorable surface reconstruction rather than structural degradation, demonstrating promising stability for extended operations. The synthetic strategy developed here can be extended to the preparation of various electrocatalytic materials, contributing to energy-efficient fabrication and sustainable development goals.