Graphitic Carbon Nitride (g-C3N4) Interface and Doping Modulation of the ZIF-67@MOG Hybrid: A Novel Strategy for Engineering Bifunctional Catalysis in Durable Zn-Air Batteries

The development of efficient, stable, and low-cost bifunctional catalysts is a key challenge for the commercial application of zinc-air batteries (ZABs). Herein, a hierarchical-structure engineering strategy is proposed, in which ZIF-67 is in situ doped and anchored onto metal-organic gels (MOG) via interfacial self-assembly to form ZIF-67@MOG. High-temperature decomposition of embedded g-C3N4 generates abundant Co-N4 sites and gas channels, yielding CoNC@NCXS/CN with bifunctional ORR/OER catalytic performance. Electrochemical tests show that the CoNC@NCXS/CN catalyst has an ORR onset potential as high as 0.978 V and a half-wave potential (E1/2) of 0.888 V, both significantly outperforming the commercial Pt/C catalyst. The OER overpotential (at 10 mA cm–2) of CoNC@NCXS/CN is 353 mV, and the bifunctional potential difference ΔE is 0.695 V comparable to Pt/C-RuO2 (0.694 V). DFT calculations further evidence that rich Co-N4 active sites derived from g-C3N4 optimize oxygen intermediate adsorption, lowering free energy barriers from 1.69 to 0.48 eV (U = 1.23 V) and accelerating ORR kinetics. The CoNC@NCXS/CN-based ZAB exhibits remarkable performance with the open-circuit voltage of 1.46 V, the maximum power density of 163.0 mW cm–2, and a high specific capacity of 764.17 mAh g–1. At a current density of 10 mA cm–2, the battery exceptional cycling durability, operating stably for 925 h (2500 chargedischarge cycles) without obvious degradation. This work proposes an effective and generalizable route to high-performance bifunctional oxygen electrocatalysts for energy conversion and storage applications.