Graceful choreography for CO ₂ and H ₂ O One challenge for efficient electrochemical reduction of carbon dioxide (CO ₂ ) is that the gas is hydrophobic, but many of its desirable reactions require water (H ₂ O). García de Arquer et al. addressed this problem by combining a copper electrocatalyst with an ionomer assembly that intersperses sulfonate-lined paths for the H ₂ O with fluorocarbon channels for the CO ₂ . 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