N‑Doped Graphene-Supported Diatomic Ni–Fe Catalyst for Synergistic Oxidation of CO

Polynary single-atom structures can provide synergistic functions based on multiple active sites and reactants, which significantly improve their catalytic performance. However, the structure–activity relationships of these special structures remain elusive. Here, we report atomically dispersed Fe–Ni dual-metal catalysts anchored on N-doped graphene as an efficient catalyst for CO oxidation. The density functional theory (DFT) calculation results show that Ni serves as a catalytic nucleophilic center for CO adsorption, whereas Fe serves as an electrophilic center for O2 adsorption, making full use of the dual-metal active sites. Thus, a heteronuclear Fe1Ni1@NGr catalyst with the synergistic effect of combining dissimilar metal atoms has better catalytic activity and lower propensity for CO poisoning than its homonuclear counterparts. Comparing the Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) mechanisms for CO oxidation on Fe1Ni1@NGr, Ni2@NGr, and Fe2@NGr, we find that the LH mechanism with coadsorbed CO and O2 is dynamically more favorable. In addition, residual oxygen atoms attached to the Fe–Ni active sites can easily react with additional CO molecules, indicating the achievement of a high recycling rate. These findings reveal a synergistic catalytic mechanism of graphene-supported atomically dispersed transition dual-metal catalysts, providing important guidance for the rational design of atomically dispersed catalysts.