Ce³⁺/Ce⁴⁺ Ion Redox Shuttle Stabilized Cu^δ+ for Efficient CO₂ Electroreduction to C₂H₄

The CO₂ electroreduction reaction has advantages in clean and pollution-free carbon conversion, but it still faces challenges in carbon utilization efficiency and improving the selectivity of C₂ products. Although the dynamic Cu^δ+ state is known to favor the C-C coupling process, the suitable Cu^δ+ species for electrocatalytic reduction of CO₂ are difficult to maintain under the conditions of strong reduction and large current. Herein, we propose a Ce doping strategy to stabilize the Cu^δ+ state (Ce/CuO_x) during the CO₂RR process, which enables a high Faradaic efficiency of 60 % for multi-carbon products (40 % for C₂H₄, 14 % for CH₃CH₂OH, and 6 % for CH₃COOH), and 25 h stability at -1.2 V versus the reversible hydrogen electrode. In situ infrared spectroscopy, in situ X-ray photoelectron spectroscopy combined with density functional theory calculations reveal that the Cu^δ+ is stabilized by the redox ion pairs of Ce, which reduces the energy barrier of *CO coupling, and improves the Faraday efficiency of electrocatalytic CO₂ reduction of C₂H₄. This work provides a new idea to make full use of lanthanide variable value metals for advanced catalysis and clean energy conversion.