Hierarchically porous architecture of metal–organic framework-derived and S induced electron localization of Fe single atom sites for boosted ORR

Abstract

Metal-organic frameworks (MOFs), with their high specific surface area, excellent stability and high electron transfer ability, are ideal supports for accommodating single metal atoms. However, the low utilisation of single-atom active sites limits the improvement of oxygen reduction reaction (ORR) performance.In this work, NH2-MIL-53(Al), a MOF possessing a mesoporous cage architecture, is used as the precursor to prepare N-doped carbon supports (denoted herein as N-HPC) with a well-defined mesoporous structure through pyrolysis. Thiourea was further employed for S doping and impregnated with a FePc, and heated again to yield Fe@S/N-HPC catalysts rich in accessible FeNx single atom sites. The porous structure is more accessible to Fe center atoms by exposing the active sites, provide easy electron conductivity and facilitate mass transport of ORR-intermediates. The prepared hierarchically porous architecture of NH2-MIL-53(Al)-derived and S induced electron localization of Fe SAs sites exhibit excellent ORR performance in alkaline (E1/2 = 0.88 V) medium.