Enhanced electrochemical CO2 reduction for high ethylene selectivity using iodine-doped copper oxide catalysts

Electrochemical CO2 reduction technology holds great promise for achieving carbon neutrality, yet the challenge of enhancing selectivity for ethylene (C2H4) production remains significant. Monovalent copper (Cu+) has been recognized for its ability to promote the formation of valuable multicarbon products, and the presence of oxygen vacancies facilitates the adsorption and activation of CO2. In this study, we present a novel approach to address this challenge by developing iodine-doped copper oxide catalysts (I-CuO) with enriched Cu+ and oxygen vacancy active sites through a one-step hydrothermal reaction method. Detailed characterization using X-ray photoelectron spectroscopy and electron paramagnetic resonance confirms that iodine doping induces the formation of Cu+ and increases the oxygen vacancy content, respectively. The designed 1.0% I-CuO catalyst demonstrates outstanding performance, achieving a faradaic efficiency of 50.2% for C2H4 formation and an overall CO2 reduction faradaic efficiency exceeding 64.8%. The remarkable C2H4 production of I-CuO is attributed to the synergistic interaction between Cu+ and oxygen vacancy. In situ Raman spectroscopy reveals that the incorporation of iodine into copper oxide effectively stabilizes Cu+ and prevents its reduction throughout the entire electrolysis process. Furthermore, I-CuO exhibits hydrophobic properties, inhibiting the competing hydrogen evolution reaction. This work not only provides valuable insights into the catalytic mechanism of electrochemical CO2 reduction using iodine-doped copper oxide catalysts but also offers a blueprint for the design of efficient metal-free doping catalysts to promote CO2 conversion and utilization.