Work

Simultaneously Boosting Graphitization and Nitrogen Doping of Carbon Catalysts for Enhanced Alkaline Oxygen Reduction Reaction Catalytic Activity

Year: 2025

Type: article

Abstract: Oxygen reduction reaction (ORR) is pivotal in energy conversion devices. Metal‐free nitrogen‐doped carbon (NC) catalysts are promising for alkaline ORR. Yet, the tradeoff between graphitization and nitrogen doping limits their catalytic activity. Herein, a strategy to enhance graphitization and nitrogen doping simultaneously by coupling hydrogen (H 2 ) gas and urea into the pyrolysis of a metal–organic framework (i.e., ZIF‐8) precursor is reported. Introducing 7.5 vol% H 2 promotes selective carbon gasification, improving graphitic structures, while urea compensates for nitrogen loss and enriches graphitic‐N. The optimized NC catalyst achieves a high half‐wave potential (0.85 V RHE ), a current density of 5.56 mA cm − 2 at 0.3 V RHE , and a low Tafel slope of 57 mV dec − 1 in 0.1 M KOH electrolyte, comparable to commercial 20 wt% Pt/C catalysts. Improved graphitization (G/D ratio of 0.973) and an increased relative abundance of graphitic‐N (20.0 at%) correlate with enhanced intrinsic catalytic activity. Furthermore, a primary zinc‐air battery using the optimized NC catalyst exhibits superior performance, delivering a maximum power density of 140 mW cm − 2 and a specific discharge capacity of 722 mAh g Zn −1 . This work presents a novel approach to designing high‐performance metal‐free carbon catalysts by tailoring pyrolysis environments to strike a balance between graphitization and nitrogen doping.

Source: ChemistryEurope

DOI: 10.1002/ceur.202500136