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.