Covalent Phenanthroline Framework Derived FeS@Fe3C Composite Nanoparticles Embedding in N-S-Codoped Carbons as Highly Efficient Trifunctional Electrocatalysts

Efficient and earth-abundant materials with multifunctional electrocatalytic properties within a wide range of pH are the new darlings for developing green energy conversion and storage techniques. A novel porous covalent phenanthroline framework (Fe-Phen-COFs) that involved Fe-DMSO (dimethyl sulfoxide) coordination complexes is successfully synthesized using 3, 8-dibromophenanthroline and 1, 3, 5-benzenetriboronicacid trivalent alcohol ester as a rigid building block via Suzuki coupling reaction. Fe-Phen-COFs as the self-carrier enriched with Fe, S, N, and C is pyrolyzed to produce N-S-codoping carbons with embedded core-shell Fe3C and FeS composite nanostructures (FeS/Fe3C@N-S-C). The FeS/Fe3C@N-S-C-800 obtained by pyrolysis at 800 degrees C exhibits efficient trifunctional electrocatalytic activity for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) within a wide pH range. Impressively, the ORR half-potential of FeS/Fe3C@N-S-C-800 reaches 0.87 V in 0.1 m KOH, more positive than the previously reported Pt-free electrocatalysts. It could be utilized as the advanced air electrode materials in zinc-air batteries, which exhibit an excellent power density and cycling stability superior to those of Pt/C-based zinc-air battery. Thermal conversion of novel Fe-Phen-COFs provides an effective strategy to prepare high-performance trifunctional electrocatalytic materials for the new-generation powerful energy conversion technologies.