“Pharaoh’s Snakes” Reaction-Derived Carbon with Favorable Structure and Composition as Metal-Free Oxygen Reduction Reaction Electrocatalyst

Abstract

Metal-air batteries rely on the oxygen reduction reaction (ORR) for their operation. However, the ORR is kinetically slow, necessitating the use of Pt-based catalysts, which is hindered by their high cost and limited availability. Consequently, considerable efforts have been dedicated to developing metal-free catalysts for the ORR. Among these, heteroatom-doped carbons have emerged as promising candidates by manipulating their composition and microstructure. Inspired by the ancient “Pharaoh’s snakes” reaction, this study utilized sugar, melamine, and a polymerizable ionic liquid as precursors to prepare heteroatom-doped carbons with the desired composition and structure. The resulting carbon catalyst exhibited an onset potential and half-wave potential in a 0.1 M KOH electrolyte that was comparable to those of a commercial Pt/C 20 wt.% catalyst, with values of 0.97 and 0.83 VRHE, respectively. Furthermore, the catalyst demonstrated excellent stability, retaining 93% of its initial current after a 10,800-s test. To evaluate its practical application, the synthesized carbon was employed as the cathode catalyst in a Zn-air battery, which achieved a maximum power density of 90 mW cm−2. This study, therefore, presents a simple yet effective method for producing metal-free heteroatom-doped carbon ORR catalysts used in various energy conversion and storage devices.