Experimental and Theoretical Insights into the Role of Iron in the Rapidly Fabricated Ni/Fe Electrodes for the Oxygen Evolution Reaction.

The development of low-cost electrocatalysts for the oxygen evolution reaction (OER) of water electrolysis is crucial for large-scale green hydrogen production. NiFe-based electrocatalysts have garnered significant attention due to their high OER activity; however, the need for a rapid and efficient electrode fabrication method and a clear understanding of the role of Fe in enhancing OER activity remains unresolved. Herein, a highly active NiFe-based OER electrocatalyst self-supported on carbon fiber paper (CFP) is developed using a versatile and rapid thermal shock method, requiring only 30 s of heat treatment. The as-prepared FeNi/CFP shows a current density of 493 mA/cm at 1.7 V vs reversible hydrogen electrode (RHE) and a low overpotential of 247 mV at 10 mA/cm, with excellent long-term durability in alkaline conditions. In situ Raman spectroscopy, pH-dependance activity test, and electronic structure calculations reveal that Fe not only promotes the oxidation of adjacent Ni but also accelerates the deprotonation of adsorbed -OH groups and stabilizes oxo-intermediates, thus, displaying both direct and indirect effects and enhancing the overall OER performance. This article provides a foundation for developing cost-effective electrocatalysts for hydrogen production and other sustainable energy applications while enhancing the understanding of the role of Fe in NiO catalysts.