Boosting the Oxygen Reduction Reaction in Zn–Air Batteries via a Uniform Trace N-Doped Carbon-Based Pore Structure

Abstract

Zn–air batteries (ZABs) have attracted significant research interest due to their low cost, high safety, and large energy density. The oxygen reduction reaction (ORR) in ZABs can be boosted by employing an effective catalyst. The construction of an ORR catalyst comparable to commercial Pt/C remains a considerable challenge without introducing metal atoms due to the sluggish reaction kinetics. Herein, a nitrogen-doped carbon-based material with a uniform porous structure was constructed by the ingenious cooperation of urea and sodium chloride. The obtained catalyst (USPC) exhibited an onset potential of 0.939 V, a half-wave potential of 0.849 V, and a limiting current of 5.72 mA cm–2 in a 0.1 M KOH electrolyte. After 5000 cyclic voltammetry cycles, the limiting current density of the USPC decreased by 0.16 mA cm–2, and there was no negative shift in the half-wave potential. The assembled ZAB displayed a maximum power density of 167 mW cm–2, with an excellent specific capacity of 782 mA h g–1 at 10 mA cm–2 and good galvanostatic discharge–charge cycling durability, which were significantly improved compared to those of Pt/C. The pore size, chemical composition, and nitrogen content were not the controlling factors for the USPC in improving the ORR performance. Doping trace amounts of nitrogen could significantly promote the onset potential (vs RHE), and the uniform and fine nanopores could effectively increase the limiting current, that is, an improvement in ORR activity. This work illustrates the importance of the origin of the catalytic activity and promotes the development of high-performance ZABs.