Copper-Zinc Bimetallic Two-Dimensional Conjugated Coordination Polymers for Highly-Selective Electrochemical CO2 Reduction to Ethanol.

Copper-based catalysts are the most promising catalysts for their ability to electrochemically prepare multi-electron C2+ products like ethanol (C2H5OH). However, the challenges persist in achieving high yields and selectivity, attributed to the unstable intermediates during the CO2 reduction reaction (CO2RR). Here, we report layer-stacked two-dimensional conjugated coordination polymers (2D c-CPs) with spatially separated Cu/Zn-S4 bi-active sites (named as BHT-Cux-Zny, x + y = 1) as electrocatalysts for addressing the above challenges of low Faradaic efficiency (FE) and subpar selectivity for ethanol production. Notably, the resultant BHT-Cu0.8-Zn0.2 2D c-CP exhibits boosting electrochemical selective conversion of CO2 to C2H5OH with a remarkable FE of 92.3 ± 2.4% at 126.7 mA cm-2 in a flow-cell, with stability maintained over 150 h, superior to the thus-far-reported Cu-based electrocatalysts. The integration of Zn enhances the catalytic activity and the interaction strength of Cu with key intermediate compounds. Benefited from the high selectivity, we further present a carbon efficiency of 73% for the conversion of CO2 to C2H5OH, along with a full-cell energy efficiency of 52%. Additionally, the energy cost is calculated at 56.6 GJ per tonne of C2H5OH, which is the lowest reported among the existing CO2 electrolysis systems for C2H5OH production.