Engineering Adjacent Cu Clusters to Modulate Single-Fe-Atom Sites for Enhanced CO₂-to-CO Electrocatalytic Conversion

Fine-tuning the coordination environment and electronic structure of metal sites in metal–nitrogen–carbon (M–N–C) catalysts is an effective strategy for boosting the activity of electrocatalytic CO₂ reduction reaction (CO₂RR), but remains challenges. Here, a negatively charged polyelectrolyte nanosphere (n-PNS)-confinement-pyrolysis strategy is developed to rationally engineer bimetallic atomic sites anchored on a hierarchical porous carbon (HPC) derived from zeolitic imidazolate framework-8 (ZIF-8). Through precise design of Cu species (single atoms, atomic clusters, and nanoparticles), the electronic and coordination structures of Fe single-atom sites are effectively tailored. Notably, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy analysis confirms that the incorporation of Cu atomic clusters (Cu_C) adjacent to isolated Fe single atoms (Fe_A) induces significant electron transfer from Fe to Cu through metal–support interactions. By virtue of this electronic modulation, the Cu_CFe_A/HPC catalyst exhibits exceptional electrocatalytic CO₂RR performance, achieving a CO Faradaic efficiency of 91% and a CO current density of 5.57 mA cm⁻², as well as remarkable durability at −0.5 V versus RHE, surpassing the Cu_C/HPC and Fe_A/HPC references. This study proposes a novel approach for designing bimetallic M–N–C catalysts to achieve efficient CO₂RR by utilizing the synergistic interactions between single atom and atomic cluster metal species.