High‐Temperature Air Synthesis: A Facile Approach to Nitrogen‐Doped, Metal‐Free Carbon Electrocatalysts

Abstract

This study presents a novel, straightforward method for synthesizing hierarchical nitrogen‐doped carbon structures, positioning metal‐free, carbon‐based materials as potential substitutes in electrochemical reactions such as oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The unique method involves a single‐step pyrolysis process in an air atmosphere, eliminating the need for an inert atmosphere and pre‐treatment procedures. It enables simultaneous self‐templating and heteroatom doping, resulting in oxygen‐rich functional groups embedded in the nitrogen‐doped carbon structure. We also crafted a carbon structure without heteroatom doping, comparing its electrochemical performance in ORR and HER. Our findings indicate that carbon catalysts pyrolyzed at higher temperatures have more pyridinic N, functional groups, and active sites‐ factors conducive to electrochemical reactions. We tested the air‐synthesized electrocatalysts for ORR in alkaline electrolyte and employed the optimized nitrogen‐doped carbon catalyst, pyrolyzed at 700 °C in an air atmosphere, as cathode material in a zinc‐air battery. This catalyst demonstrated ORR performance comparable to the commercial Pt/C catalyst and showed minimal overpotential in acidic HER. Our research establishes a pioneering technique for synthesizing porous, metal‐free, nitrogen‐doped carbon materials, paving the way for potential energy applications.