Hierarchical N-Doped Porous Carbons for Zn–Air Batteries and Supercapacitors

Nitrogen-doped carbon materials with a large specific surface area, high conductivity, and adjustable microstructures have many prospects for energy-related applications. This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction (ORR) and supercapacitors. Here, we report a low-cost, environmentally friendly, large-scale mechanochemical method of preparing N-doped porous carbons (NPCs) with hierarchical micro-mesopores and a large surface area via ball-milling polymerization followed by pyrolysis. The optimized NPC prepared at 1000 °C (NPC-1000) offers excellent ORR activity with an onset potential (E(onset)) and half-wave potential (E(1/2)) of 0.9 and 0.82 V, respectively (vs. a reversible hydrogen electrode), which are only approximately 30 mV lower than that of Pt/C. The rechargeable Zn–air battery assembled using NPC-1000 and the NiFe-layered double hydroxide as bifunctional ORR and oxygen evolution reaction electrodes offered superior cycling stability and comparable discharge performance to RuO(2) and Pt/C. Moreover, the supercapacitor electrode equipped with NPC prepared at 800 °C exhibited a high specific capacity (431 F g(−1) at 10 mV s(−1)), outstanding rate, performance, and excellent cycling stability in an aqueous 6-M KOH solution. This work demonstrates the potential of the mechanochemical preparation method of porous carbons, which are important for energy conversion and storage. [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s40820-019-0364-z) contains supplementary material, which is available to authorized users.