Abstract
Carbon-supported iron-cobalt bimetallic electrocatalysts usually exhibit robust catalytic activity toward the oxygen evolution reaction (OER). However, the spatial isolation of Fe species at atomic level on cobalt-carbon solid remains a great challenge for practical catalytic applications in the OER. Here, we report the fabrication of CoFe bimetal porous carbon electrocatalysts by pyrolysis of molecularly defined iron complexes such as FePc (Pc = phthalocyanine) and Fe(acac)(3) pre-encapsulated in the cavities of zeolitic imidazolate framework (ZIF)-67. With this unique strategy, high-loading atomic Fe nanoclusters (Fe-ACs) and Fe single atoms (Fe-SAs) were supported on Co/NC hybrids relying on the size of the molecular Fe precursors. The former exhibited superior OER performance to the single Fe atom-decorated Co/NC, as well as other ZIF-67-derived electrocatalysts. Theoretical modulation suggests Co as the OER active site for Fe-ACs@Co/NC at the in situ-formed FeOOH-ACs/Co(3)O(4) interface, while Fe was proposed as the active site for Fe-SAs@Co/NC.