Mesopore-dominated N, S co-doped carbon as advanced oxygen reduction reaction electrocatalysts for Zn-air battery

Oxygen reduction reaction (ORR) is a crucial step for Zn-air batteries (ZABs), which requires low-cost yet efficient catalysts to satisfy the practical application. Heteroatom-doped, especially N, S-doped carbon, has attracted intensive attention as promising ORR catalysts. However, the issues of devitalized micropore channels covered by reaction intermediates and unstable configuration of N, S heteroatoms obtained by post-doping treatment have largely hindered the development of carbon-based catalysts. Herein, mesopore-dominated N, S co-doped hierarchical carbon has been constructed by the hard-soft (SiO 2 –ZnCl 2 ) template strategy based on waste biomass. The optimal catalyst (NSC-PT-0.1) exhibits a mesopore-dominated hierarchical porous structure with high S BET (2357.55 m 2  g −1 ) and N, S content (~ 2.32 at.%), resulting in comparable ORR activity in acid ( E 1/2  = 0.69 V) and alkaline ( E 1/2  = 0.83 V) media to Pt/C. Moreover, different biomass precursors of Carrot, Whorled stonecrop, and Ginkgo leaf have been explored to verify the generality of hard-soft template strategy. When NSC-PT-0.1 is applied as the air electrode, the assembled ZAB exhibits high power density of 155.55 mW cm −2 and long-term cycling stability over 216 h. Therefore, this work provides a versatile hard-soft template strategy to synthesize efficient ORR catalysts for ZABs application through the resource utilization of biomass. Graphical abstract Mesopore-dominated N, S co-doped carbon is synthesized by one-step pyrolysis of waste biomass and SiO 2 –ZnCl 2 hard-soft templates. The optimal catalyst exhibits excellent ORR performances in alkaline and acid media as well as promising Zn-air battery application.