Al-Rich Cu/CuOx Catalyst in a CO2-Reduction Tandem Electrolyzer with CO-Enriched Gas Feed for Enhanced C2+-Products Selectivity

Electrochemical CO₂ conversion is an important strategy to produce high-value carbon-containing molecules, such as ethylene and ethanol. Despite huge progress in recent years concerning CO₂ reduction catalyst development with increased selectivity, high selectivity for C₂₊ products at high current densities is still a challenge. We report the development and optimization of a new surface Al-rich Cu/CuO_x catalyst with high selectivity for C₂₊-products at high current densities of up to −800 mA cm⁻². We integrated the corresponding catalyst-modified gas-diffusion electrode into a second flow-through electrolyzer, which was connected to a first flow-through electrolyzer comprising a highly CO-selective Ni−Cu dual-atom N-doped carbon catalyst. The enrichment of the CO₂ stream with CO generated at a current density of −400 mA cm⁻² in the first electrolyzer increased the production rate of ethanol formation at the Al-rich Cu/CuO_x catalyst at a current density of −300 mA cm⁻² by 28 %, while maintaining the production rate of ethylene. Thereby, the overall yield of C₂₊-products obtained by CO₂ reduction was significantly increased.