CO2 electrolysis to multicarbon products at activities greater than 1 A cm−2

Graceful choreography for CO2 and H2O One challenge for efficient electrochemical reduction of carbon dioxide (CO2) is that the gas is hydrophobic, but many of its desirable reactions require water (H2O). García de Arquer et al. addressed this problem by combining a copper electrocatalyst with an ionomer assembly that intersperses sulfonate-lined paths for the H2O with fluorocarbon channels for the CO2. The electrode architecture enables production of two-carbon products such as ethylene and ethanol at current densities just over an ampere per square centimeter. Science, this issue p. 661 Electrode architecture reconciles the hydrophobic nature of CO2 with the need for nearby water to reduce it to ethylene. Electrolysis offers an attractive route to upgrade greenhouse gases such as carbon dioxide (CO2) to valuable fuels and feedstocks; however, productivity is often limited by gas diffusion through a liquid electrolyte to the surface of the catalyst. Here, we present a catalyst:ionomer bulk heterojunction (CIBH) architecture that decouples gas, ion, and electron transport. The CIBH comprises a metal and a superfine ionomer layer with hydrophobic and hydrophilic functionalities that extend gas and ion transport from tens of nanometers to the micrometer scale. By applying this design strategy, we achieved CO2 electroreduction on copper in 7 M potassium hydroxide electrolyte (pH ≈ 15) with an ethylene partial current density of 1.3 amperes per square centimeter at 45% cathodic energy efficiency.