The Fe sites in non-precious metal nanocatalysts toward efficient water oxidation

Water electrolysis is a pivotal technology for renewable hydrogen production. Iron (Fe), due to its abundant reserves, low cost, versatile valence states, tunable coordination structures, and co-friendliness under alkaline conditions, is a key alternative to precious metals as a catalytic center. Although extensive studies have demonstrated that Fe sites can significantly boost the oxygen evolution reaction (OER) performance of non-precious metal catalysts, there is still no profound understanding of the intrinsic role of Fe sites in the OER process. This paper systematically reviews the core function of Fe sites in nanocatalysts during water electrolysis, including their electronic and spin structures, catalytic behaviors and fundamental reaction mechanisms. It addresses how electronic structure, valence evolution and coordination environment regulate intermediate adsorption, desorption barriers and reaction pathways, and summarizes typical strategies for introducing Fe sites and optimizing catalytic activity and stability. Moreover, the advanced characterization for identifying active-site evolution is also highlighted. Finally, the challenges facing Fe sites in catalysis and the corresponding solutions are analyzed and an outlook on the rational design and large-scale application of non-precious metal catalysts via Fe introduction is presented.