Coupling of Mn–Nx Sites with Abundant Defective Carbon for Enhanced Oxygen Electroreduction in Quasi-Solid-State Zinc–Air Batteries

The integration of Mn–N_x sites with defective carbon can significantly enhance the oxygen reduction reaction (ORR) activity of carbon-based catalysts. Herein, wheat straw is molecularly assembled with Mn source and nitrogen-rich compounds to generate a macromolecular precursor through hydrogen bonding and promote the dispersion of Mn-related species. The Mn–N_x sites anchored on wheat straw-derived porous carbon can be synthesized during high-temperature pyrolysis. Meanwhile, the macromolecular precursor can produce nitrogen-related and carbon-related gases to form defective carbon (r-Mn/N-WSPC). Rich Mn–N_x sites can serve as effective ORR sites on r-Mn/N-WSPC. Abundant defective carbon can optimize the electronic structure of Mn–N_x sites, adjust O₂ adsorption energy to a moderate state, and reduce the energy barrier. The r-Mn/N-WSPC exhibits a large specific surface area of 1667.53 m² g^–1 and an ORR half-wave potential of 0.921 V (vs RHE). With r-Mn/N-WSPC as the cathode catalyst, the excellent performance of quasi-solid-state zinc-air batteries (ZABs) with a specific capacity of 639.74 mA h g^–1, a power density of 36.16 mW cm^–2, and a long-term charge–discharge cycle stability of about 28 h can be obtained. The performance exploration of r-Mn/N-WSPC contributes to the efficient development and applications of wheat straw-derived carbon in quasi-solid-state ZABs.