Regulating Cu Oxidation State for Electrocatalytic CO₂ Conversion into CO with Near‐Unity Selectivity via Oxygen Spillover

Abstract Cu‐based catalysts are the most intensively studied in the field of electrocatalytic CO₂ reduction reaction (CO₂RR), demonstrating the capacity to yield diverse C₁ and C₂₊ products albeit with unsatisfactory selectivity. Manipulation of the oxidation state of Cu sites during CO₂RR process proves advantageous in modulating the selectivity of productions, but poses a formidable challenge. Here, an oxygen spillover strategy is proposed to enhance the oxidation state of Cu during CO₂RR by incorporating the oxygen donor Sb₂O₄. The Cu‐Sb bimetallic oxide catalyst attains a remarkable CO₂‐to‐CO selectivity approaching unity, in stark contrast to the diverse product distribution observed with bare CuO. The exceptional Faradaic efficiency of CO can be maintained across a wide range of potential windows of ≈700 mV in 1 m KOH, and remains independent of the Cu/Sb ratio (ranging from 0.1:1 to 10:1). Correlative calculations and experimental results reveal that oxygen spillover from Sb₂O₄ to Cu sites maintains the relatively high valence state of Cu during CO₂RR, which diminishes the binding strength of ^*CO, thereby achieving heightened selectivity in CO production. These findings propose the role of oxygen spillover in CO₂RR over Cu‐based catalysts, and shed light on the rational design of highly selective CO₂ reduction catalysts.