A very basic pathway from CO ₂ to ethylene: Ethylene is an important commodity chemical for plastics. It is considered a tractable target for synthesizing renewably from carbon dioxide (CO ₂ ). The challenge is that the performance of the copper electrocatalysts used for this conversion under the required basic reaction conditions suffers from the competing reaction of CO ₂ with the base to form bicarbonate. Dinh et al. designed an electrode that tolerates the base by optimizing CO ₂ diffusion to the catalytic sites (see the Perspective by Ager and Lapkin). This catalyst design delivers 70% efficiency for 150 hours. Science , this issue p. 783 ; see also p. 707

Modulating metal oxides: The more difficult step in fuel cells and water electrolysis is the oxygen evolution reaction. The search for earth-abundant materials to replace noble metals for this reaction often turns to oxides of three-dimensional metals such as iron. Zhang et al. show that the applied voltages needed to drive this reaction are reduced for iron-cobalt oxides by the addition of tungsten. The addition of tungsten favorably modulates the electronic structure of the oxyhydroxide. A key development is to keep the metals well mixed and avoid the formation of separate phases. Science , this issue p. 333

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