ZIF-8-Derived N-Doped Hierarchically Porous Carbon-Supported Mn Nanoparticles Toward Oxygen Reduction for Zn–Air Batteries

The development of cost-effective, high-performance oxygen reduction reaction (ORR) electrocatalysts is pivotal for advancing energy conversion technologies such as metal–air batteries and fuel cells. Herein, we report a facile and efficient strategy to synthesize Mn nanoparticles loaded on N-doped hierarchically porous carbon framework (Mn/N-C) through utilizing ZIF-8 as a carbon/nitrogen precursor and MnCl 2 ·4H 2 O as the Mn source. The synthesis integrates mechanical grinding with an NaCl-assisted pyrolysis process, where molten NaCl acts as a dynamic template and intercalation agent to prevent structural collapse during carbonization, thereby creating a 3D porous architecture with coexisting micro-, meso-, and macropores. Physicochemical characterization reveals that the Mn/N-C-2 sample exhibits a high specific surface area (1770 m 2 /g), abundant defects, and uniform dispersion of Mn nanoparticles within the N-doped carbon matrix. Electrochemical evaluations demonstrate that Mn/N-C-2 catalyst possesses a higher half-wave potential ( E 1/2 ) of 0.836 V and a larger limiting current density ( J L ) of 5.54 mA/cm 2 , surpassing other control samples and most reported Mn-based catalysts and comparable to that of commercial Pt/C. When integrated into Zn–air batteries (ZABs), Mn/N-C-2-based ZABs deliver an open-circuit voltage of 1.49 V and a peak power density of 150.51 mW/cm 2 , outperforming benchmark Pt/C-based counterparts. This work offers a cost-effective electrocatalyst for ORR and can be used instead of noble metals in ZABs. Graphical Mn/N-C electrocatalysts are fabricated by a NaCl-assisted pyrolysis strategy. The optimized Mn/N-C-2 catalyst exhibits a large specific surface area, hierarchically porous architecture and high content of active N, presenting an E 1/2 of 0.836 V for ORR. When integrated into ZABs, it delivers an open-circuit voltage of 1.49 V and a peak power density of 150.5 mW/cm 2 .