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

Potassium helps CO ₂ compete in acid: Electrochemical reduction of carbon dioxide (CO ₂ ) is a promising means of converting this greenhouse gas into valuable fuels and chemicals. However, two competing reactions restrict the efficiency of this process. In base, much of the CO ₂ is trapped as carbonate before reduction; in acid, protons outpace CO ₂ at catching electrons from the cathode. Huang et al. report that a high dose of potassium ions can help to solve the latter problem. By concentrating potassium ions at the electrode, high selectivity toward CO ₂ reduction at high current in acid is possible, which the authors attribute to electrostatic stabilization of the desired adsorbates. Science , abg6582, this issue p. 1074