Selective Electroreduction of CO2 to Ethanol via Cobalt–Copper Tandem Catalysts

The selective electrocatalytic conversion of CO2 into multicarbon products, such as ethanol, is a major technological challenge. Currently, this reactivity is limited by the sluggish formation of C–C bonds inherent to many single-site catalysts. Here, we report a new tandem electrocatalyst based on earth-abundant elements, which facilitates the selective CO2-to-ethanol conversion. The composite catalyst consists of neighboring cobalt and copper atoms anchored to electrically conductive nitrogen-doped carbon. At low overpotentials (E = −0.8 V vs reversible hydrogen electrode), the system shows high selectivity for ethanol production (faradaic efficiencies >70%), while retaining its reactivity and stability for 18 h. A CO spillover mechanism is proposed as the basis for the observed selectivity, where efficient CO generation at Co sites leads to high local CO concentrations at neighboring Cu sites, thereby favoring C–C coupling and ethanol formation. Operando X-ray absorption spectroscopy reveals a dynamic transformation of the single-site Cu into Cu clusters as actual active sites. In situ infrared spectroscopy reveals the formation of intermediate CO at Co sites, which undergo subsequent spillover and C–C coupling on the Cu clusters. This design concept offers new avenues for noble metal-free tandem electrocatalysts for the conversion of CO2-to-multicarbon products.