Atomically Dispersed Fe-N₅ Sites Anchored in Porous N-Doped Carbon Nanofibers for Effective Hydrogen Evolution Reaction

Atomically dispersed electrocatalysts are a major focus of chemical and energy conversion, while the structure and hydrogen evolution reaction (HER) performance affected by single atoms loading need to be further explored. Herein, we developed an N-coordination strategy to design Fe-N₅sites distributed on N-doped porous nanofibers (Fe SA/PNCNFs-0.1) as an efficient HER catalyst by the wet impregnation method. The results show that Fe species exist in the form of dispersed single atoms. The binding between the Fe atom and N atom is strong, forming the coordination structure of Fe-N₅. In the acidic HER, Fe SA/PNCNFs-0.1 improves the catalytic performance toward the HER with a small overpotential of 44.3 mV at 10 mA cm^-2current density and a low Tafel slope of 45.4 mV dec^-1, which are superior to those of Fe single atoms with less Fe contents (Fe SA/PNCNFs-0.4) and Fe nanoparticles (Fe NP/PNCNFs). Fe SA/PNCNFs-0.1 also has excellent HER activity and durability in alkaline media, highlighting the potential application of Fe single atoms for hydrogen production.