Facile synthesis of polyacrylonitrile-based N/S-codoped porous carbon as an efficient oxygen reduction electrocatalyst for zinc-air batteries

Polyacrylonitrile (PAN) is an attractive precursor for N-doped porous carbons owing to its high nitrogen content and good thermal stability. Herein, a facile and effective route for the synthesis of N/S co-doped porous carbon by capitalizing on hetero-atom containing PAN as a doped carbon source and ZnCl₂ as a volatile porogen is reported. Notably, the optimal porous carbon (denoted as FeZ-CNS-900) with a large specific surface area of up to 1730 m² g^-1 exhibits excellent oxygen reduction reaction (ORR) activity with a half-wave potential of 0.881 V, which is 39 mV more positive than that of commercial Pt/C under alkaline conditions, as well as robust durability and methanol tolerance. Interestingly, the use of N/S co-doped porous carbon also offers comparable ORR activity yet much higher stability than that of Pt/C under acidic conditions. Finally, the implementation of FeZ-CNS-900 as the air-cathode catalyst for primary Zn-air batteries yields an open-circuit potential of 1.49 V, a high peak power density of 168 mW cm^-2, a large specific capacity of 778 mA h g_Zn^-1 (corresponding to an energy density of 1020 W h kg_Zn^-1) and a remarkable durability.