A new steric tetra-imidazole for facile synthesis of high loading atomically dispersed FeN4 electrocatalysts

Highlights: • A novel steric tetra-imidazole structure for synthesis of atomically dispersed FeN₄ electrocatalysts. • Atomic iron content reaches up to 2.58 wt% without any post-/pre-treatment. • This one-step approach endows facile scale-up synthesis of high loading atomic dispersed Fe-N-C. Atomically dispersed FeN₄ rich carbon-based electrocatalysts obtained by pyrolysis of Zn-based metal-organic frameworks (mainly Fe modified ZIF-8) exhibits remarkable catalytic performance for oxygen reduction reaction (ORR). However, the independence of each ZIF-8 particle with rhomb dodecahedral results in a physical stack and undesirable charge transfer path and subsequently induce the iron buried in the carbon matrix after the pyrolysis process, which further impedes the high loading of atomic iron (usually less than 1 wt%). Herein, we newly designed a novel steric tetra-imidazole structure to anchor iron in a cross way. This strategy achieves the synthesis of atomically dispersed FeN₄ rich carbon-based electrocatalyst in one-step approach without any pretreatment and/or further acid leaching. Unlike the traditional imidazole in ZIF-8, the novel steric tetra-imidazole structure exhibits a benzene ring located in the center of each four imidazole groups acting as sharing side-chain substitution, which can control the distance of each metal rivet center and impede the aggregation of iron effectively. The obtained catalyst, named as TimB-Fe₅-C, exhibits high atomic iron loading content up to 2.58 wt% and exhibits efficient ORR electrocatalytic performance in both alkaline and acid medium. Significantly, this new steric tetra-imidazole endows one-step facile synthesis of atomically dispersed electrocatalysts with high loading and to avoid unpredictable changes of structure brought by tedious pre-treatment as well as post-treatment.