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 (E1/2 = 0.930 V, Ej: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.