Manganese-Assisted Annealing Produces Abundant Macropores in a Carbon Aerogel to Enhance Its Oxygen Reduction Catalytic Activity in Zinc–Air Batteries
Yanhua Pang, Zaiyong Mo, Hui Wang, Xuyun Wang, Vladimir Linkov, Rongfang Wang
Abstract
Carbon aerogels have large specific surface areas suitable for the formation of large numbers of exposed catalytically active sites for oxygen reduction reaction (ORR). In this study, as-prepared carbon aerogels undergo a manganese-assisted annealing process, resulting in a 754 m2 g–1 specific surface area, abundant macropores, and a fourfold increase in the surface nitrogen content. An optimized Mn–N codoped carbon aerogel, with a 1:10 mass ratio of MnCl2·4H2O to carbon, annealed at 800 °C, exhibited excellent ORR catalytic activity in a three-electrode system, reaching an onset potential of 0.988 V, slightly higher than 0.975 V of commercial Pt/C (20 wt %, Johnson Matthey). A primary zinc–air battery utilizing this non-noble metal-containing material as an ORR cathode catalyst, operating at a current density of 100 mA cm–2, demonstrated an open-circuit voltage, output voltage, and power density of 1.467 V, 1.124 V, and 112.38 mW cm–2, respectively, 11 mV, 97 mV, and 9.75 mW cm–2 higher than those values of a Pt/C-containing zinc–air battery. Excellent ORR performance of the Mn–N codoped carbon aerogel could be resulting from the synergistic effect of abundant macropores, high-density nitrogen-based catalytically active sites, and a certain amount of MnO catalytically active sites.