Dual Doping Induced Interfacial Engineering of Fe2N/Fe3N Hybrids with Favorable d‐Band towards Efficient Overall Water Splitting

Abstract Interfacial engineering and electronic modulation are some of the main components for enhancing the catalytic activity of electrocatalysts towards achieving efficient water splitting. Iron nitrides exhibit mediocre oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) due to their unsuitable d‐band energy level. In this work, we strongly boost the HER and OER catalytic performance of Fe 2 N for the first time by doping Co and Al, which could not only induce the formation of Fe 2 N/Fe 3 N hybrid interface but also tune the d‐band center position. The CoAl−Fe 2 N/Fe 3 N nanoparticles display HER and OER overpotential of 145 and 307 mV at 10 mA/cm 2 . XPS and DFT calculations confirm that tailoring the d‐band center position and interfacial engineering facilitates strong electronic interactions between Fe 2 N and Fe 3 N, synergistically optimize the electronic structure, which enriches H and H 2 O adsorption energy and oxygen‐containing intermediates. An alkaline electrolyzer based on CoAl−Fe 2 N/Fe 3 N requires an overall potential of 1.67 V at 10 mA/cm 2 , demonstrating the use of iron nitrides as a bifunctional electrocatalyst for water splitting activity.