Single-atomic Fe sites modulated by Sn regulator for enhanced electrochemical CO2 reduction

Single-atom Fe catalysts show significant promise in the electrocatalytic reduction of CO₂ (CO₂RR), while their performance remains inferior to that of precious metal catalysts due to the overly strong binding of *CO intermediates. Although the introduction of heteroatoms or transition metal sites can modulate the binding strength of *CO on Fe sites, these regulators often induce competitive hydrogen evolution reaction (HER) with reduced Faraday efficiency (FE). In this work, we employ HER-inert Sn as a regulator to tune the electronic structure of Fe, weakening *CO adsorption and enhancing CO₂RR performance. Diatomic Fe-Sn pairs supported on N-doped carbon (Fe-Sn/NC) were synthesized, achieving FE for CO exceeding 90% over a broad potential range from −0.4 to −0.9 V versus the reversible hydrogen electrode. Fe-Sn/NC shows a high turnover frequency of 1.5 × 10⁴ h⁻¹, much higher than that of Fe/NC. Characterization results and theoretical calculations demonstrate that bonding Sn site to Fe generates electron-rich Fe centers, effectively reducing the adsorption strength of *CO without triggering HER. Additionally, Fe-Sn/NC exhibits exceptional activity in hydrazine oxidation performance (HzOR). The HzOR-assisted CO₂RR system using Fe-Sn/NC as electrodes reduces energy consumption by 38% compared with the conventional CO₂RR coupled oxygen evolution reaction system.