N-doped carbon nanosheets with ultra-high specific surface area for boosting oxygen reduction reaction in Zn-air batteries

When designing carbon-based electrocatalysts as Pt-free catalysts for the oxygen reduction reaction (ORR), pore structures is crucial, in addition to creating active sites. Here, N-doped carbon nanosheets were rationally designed by tactfully introducing nitrogen source into the carbonization process, which could increase the density of pore structures and effective active sites. Owing to the ultra-high specific surface area (2127 m² g⁻¹), large pore volume (5.77 cm³ g⁻¹), and bimodal-pore structure (micropores and mesopores), the optimized catalyst exhibited an excellent ORR activity (a half-wave potential of 0.86 V), as well as outstanding durability and methanol tolerance in alkaline medium. Moreover, it provided excellent stability and high peak power density when used as ORR catalyst in Zn-air battery, exceeding that driven by Pt/C catalyst. This work brings a feasible and universal strategy for fabricating metal-free ORR catalysts.