Boosting zinc-air battery performance through interface-engineered N-C/g-C₃N₄ photoelectric synergy

The direct integration of solar energy into zinc-air batteries (ZABs) provides a promising strategy for developing sustainable and high-performance energy storage systems. However, designing light-enhanced ZABs with efficient solar-energy utilization remains a significant scientific challenge. To address this challenge, a nitrogen-doped carbon/graphitic carbon nitride (N-C/g-C₃N₄) composite photoelectrocatalyst was fabricated through mechanical ball-milling. Mechanical ball-milling enabled intimate interfacial coupling between NC and g-C₃N₄, thereby inducing interfacial electronic redistribution and facilitating charge transfer. Photoelectrochemical characterization, together with VB-XPS analysis, suggests that the N-C/g-C₃N₄ interface promotes photogenerated electron transfer from g-C₃N₄ to the conductive NC network while improving the utilization of photogenerated carriers. When used as the air cathode for ZABs, the composite exhibited strong bifunctional catalytic activity under illumination. Specifically, it exhibited an oxygen reduction reaction (ORR) half-wave potential (E_1/2) of 0.90 V and an oxygen evolution reaction (OER) overpotential of 501 mV. As a result, the assembled zinc-air battery (ZAB) achieved an open-circuit voltage (OCV) of 1.50 V, a peak power density of 572.9 mW cm^-2, a specific capacity of 720 mAh g^-1, and stable cycling for over 700 h. These results demonstrate the potential of interface-engineered dual‑carbon-based photoelectrocatalysts for high-efficiency solar-assisted metal-air batteries.