Unlocking the porosity of Fe–N–C catalysts using hydroxyapatite as a hard template en route to eco-friendly high-performance AEMFCs

Abstract

In this work, we propose hydroxyapatite (HA) as a hard template to unlock the porosity of Fe–N–C catalyst materials. Using HA, a naturally occurring mineral that can be removed with nitric acid, in the synthesis generates a catalyst material with a unique porous network comprising abundant pores and interparticle cavities ranging from 10 to 3000 nm. Hard templating with HA alongside ZnCl2 as a micropore former results in a Fe–N–C catalyst based on naturally abundant peat with excellent oxygen reduction activity in alkaline conditions. A half-wave potential of 0.87 V vs RHE and a peak power density of 1.06 W cm−2 were achieved in rotating ring disk electrode and anion exchange membrane fuel cell experiments, respectively, rivaling the performance of other state-of-the-art platinum-free catalysts presented in the literature. A combined approach of using renewable peat as a carbon source and HA as a hard template offers an environmentally friendly approach to high-performance Fe–N–C catalysts with abundant porosity.