RESUMEN
Platinum group metal (PGM)-free electrocatalysts have emerged as promising alternatives to replace Pt for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, traditional synthesis methods limit the single-atom site density due to metal agglomeration at higher temperatures. This work explores the preparation of hierarchically porous atomically dispersed electrocatalysts for the ORR. The materials were prepared via ionothermal synthesis, where magnesium nitrate was used to prepare hierarchically porous carbon materials. The in-situ formed Mg-Nx sites were trans-metalated to yield ORR-active Fe-Nx sites. The resulting carbon-based catalysts displayed excellent electrocatalytic activity, attributed to the atomically dispersed Fe-Nx active sites and high meso- and macroporosity that enhances the mass transport and exposes more accessible active sites.
RESUMEN
Highly active electrocatalysts for electrochemical oxygen reduction reaction (ORR) were prepared by high-temperature pyrolysis from 5-methylresorcinol, Co and/or Fe salts and dicyandiamide, which acts simultaneously as a precursor for reactive carbonitride template and a nitrogen source. The electrocatalytic activity of the catalysts for ORR in alkaline solution was studied using the rotating disc electrode (RDE) method. The bimetallic catalyst containing iron and cobalt (FeCoNC-at) showed excellent stability and remarkable ORR performance, comparable to that of commercial Pt/C (20 wt%). The superior activity was attributed to high surface metal and nitrogen contents. The FeCoNC-at catalyst was further tested in anion exchange membrane fuel cell (AEMFC) with poly-(hexamethyl-p-terphenylbenzimidazolium) (HMT-PMBI) membrane, where a high value of peak power density (Pmax = 415 mW cm-2) was achieved.