Selective Reduction of CO₂ to CO on an Sb-Modified Cu Electrode: Spontaneous Fabrication and Physical Insight

Electrochemical CO 2 reduction reaction (CO 2 RR) on Cu is often plagued by low selectivity and stability because of less-controlled preparation of electrocatalytic materials as well as insufficient understanding of the structure–performance relation. In this work, we develop a facile galvanic displacement protocol, involving an electropolished Cu sheet in a mixed Sb(III)–Cl – precursor solution, to form an Sb-modified Cu electrode that can selectively convert CO 2 to CO with a Faradaic efficiency of ca. 82% and an undecayed reduction current over 12 h. Moreover, in situ infrared spectroscopy detects a relatively weak and red-shifted CO band on the Sb-modified Cu electrode as compared to that on the Cu electrode at potentials of CO 2 RR. Density functional theory calculations reveal that the Sb clusters on the Cu surface change the electronic structures of Cu as well as Sb and thus weaken the CO binding strength on Cu sites, consistent with the observed CO band feature and high CO selectivity. These findings may shed light on the rational design of high-selectivity CO 2 RR electrocatalysts by proper interfacial structure engineering.