Photo-electroactive p-n heterojunction catalyst with dual Co sites for high-performance light-enhanced zinc–air batteries

Highly electrocatalytic and durable Co-Nx-C frameworks containing carbon nanofibers (CNFs)/carbon nitrides (CNs) are vital materials for rechargeable zinc–air batteries (RZABs). However, the existing Co-Nx-C frameworks experience severe agglomeration during synthesis and limited active site accessibility/mechanical robustness. In this work, a photo-enhanced bifunctional catalyst with a type II p-n heterojunction (g–C₃N₄–Co@CNT/Co–N₄/C@CNF) is achieved through a combined “electrospinning + calcination + ball milling” approach. The composite integrates graphitic carbon nitride (g-C₃N₄) nanosheets with dual active Co sites (nanoparticles and Co–N₄ single atoms) anchored on conductive carbon nanofibers. This architecture enables efficient charge separation, enhanced light absorption, and accelerated oxygen redox kinetics. DFT calculations reveal that g-C₃N₄ modulates the electronic structure and lowers the reaction free-energy barriers, leading the d-band center closer to the Fermi level. Under light irradiation, the g–C₃N₄–Co@CNT/Co–N₄/C@CNF exhibits outstanding ORR/OER catalytic performance, with a small overpotential gap of 0.684 V (E_1/2 = 0.930 V, E_j:10 = 1.614 V). In practical application: 1) light-enhanced liquid ZABs with g–C₃N₄–Co@CNT/Co–N₄/C@CNF photoactive catalysts manifest a peak power density of 310 mW cm⁻² and a long cycle life exceeding 1100 h. 2) Light-enhanced flexible ZABs also can reach a peak power density of 96 mW cm⁻² and tolerate a wide range of bending angles (0°–180°–0°) during harsh operation. This work offers a new platform for designing efficient photo-electrocatalysts and advancing next-generation solar–electrochemical energy conversion systems.