High-valent iron single-atom catalysts for improved overall water splitting via a reduced energy barrier and stabilization of the active center

Abstract

The design of earth-abundant and non-precious transition-metal-based single-atom catalysts (TM-SACs) for promoting the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is of great importance for generating green hydrogen (H₂). Herein, we demonstrate iron (Fe) single atoms stabilized on carbon–nickel nanosheets (C–Ni) (Fe-SACs|C–Ni NSs) using a facile and single-step metal–organic-framework (MOF)-assisted electrochemical approach. Single-atom iron sites (Fe⁴⁺ active center), generated in situ on the C–Ni heterostructure, assist in regulating the binding abilities of hydroxyl ions (OH*) and hydrogen (H*) to accelerate alkaline water splitting reactions. Overpotentials (η) of ∼246 mV and ∼164 mV are required to reach ∼10 mA cm⁻² for the OER and HER, respectively, outperforming other recently reported bifunctional catalysts.