Atomic-level insights into bioinspired Fe/Ni bimetallic active sites on carbon nitrides for electrocatalytic O₂ evolution

Atomically dispersed active speices on nanomaterials have shown greate promise for various catalytic reactions. In this work, bioinspired bimetallic materials (FeNi-CN) are produced through the mixing of melamine with FeCl₂·4H₂O and NiCl₂·6H₂O followed by heat treatment. FeNi-CN exhibits exceptional electrocatalytic activity with an overpotential of 250 mV for oxygen evolution reactions (OERs), which surpasses the well-known IrO₂. Additionally, it shows excellent cyclic durability up to 10,000th cycle. The various characterizations reveal the atomically dispersed Fe and Ni atoms across C₃N₄ networks through coordination to N atoms. Comparative experiments with monometallic samples show that bimetallic FeNi-CN outperforms them. Density functional theory calculations support these findings, indicating that Ni has a higher OER activity than Fe, and the combination of bimetallic Ni and Fe and structural corrugation in FeNi-CN enhances catalytic performance. Ex-situ study supports the electrochemical stability. This work suggests the potential of bimetallic catalysts for electrocatalytic application.