Active sites engineering on FeNi alloy/Cr₃C₂ heterostructure for superior oxygen evolution activity

Exploring high active electrocatalysts for oxygen evolution reaction (OER) is of great significance for a sustainable hydrogen economy. The development of non-precious transition metals, with sufficient active sites and ample intrinsic activity, remains a challenge. Herein, a new type of FeNi–Cr₃C₂ heterostructure anchored on carbon sheets (FeNi–Cr₃C₂@C) was reported, which can effectively catalyze OER with swift kinetics and outstanding intrinsic activity. The introduced Cr₃C₂ phase not only serves as a support material but also effectively suppresses the thermal coarsening of FeNi alloy nanoparticle. The FeNi–Cr₃C₂@C displays a robust OER activity with a low overpotential of 283 mV at the current density of 10 mA cm⁻², a high turnover frequency value of 1.69 s⁻¹ at the overpotential of 300 mV (10 times higher than that of FeNi@C) and good stability in alkaline media. Density functional theory calculations (DFT) calculations show that Cr₃C₂ can facilitate the generation of electron-rich region at the Ni site in FeNi alloys as an active site, exhibiting an optimized adsorption behavior toward oxygen intermediate species with regard to decreased thermodynamic energy barriers. Our work opens up a promising path to modulate the electrocatalytic active sites using inexpensive and durable Cr₃C₂ for electrochemical catalytic reactions.