In the ongoing drive to reduce atmospheric levels of greenhouse gases, researchers worldwide are developing catalytic methods for converting carbon dioxide to valuable products, especially ones with more than one carbon atom. Conventional catalytic hydrogenation, which reacts gaseous CO2 and hydrogen over a solid catalyst, can do the trick. But that process typically runs at high pressures and temperatures and produces a wide distribution of products, requiring costly follow-up steps. Solution-phase electrochemical methods using a catalytic electrode and water can convert CO2 under near-ambient conditions. But like thermal catalysis, electrocatalysis also tends to generate a large collection of C1, C2 and longer products, and it often uses electrical energy inefficiently. Aiming to improve the process, a team led by Xiamen University’s Qinghong Zhang, Jun Cheng, and Ye Wang searched for ways to boost the performance of copper-based catalysts, currently among the best for electroreduction of CO2. The team made several halogen-doped copper catalysts and found that one made with ammonium bifluoride generated mainly ethylene and ethanol with roughly 86% selectivity at an electrical efficiency of 80%, outperforming previously reported catalysts (Nat. Catal. 2020, DOI: 10.1038/s41929-020-0450-0). The team explains that fluorine promotes water dissociation, generating hydrogen atoms that convert adsorbed CO to CHO species, which then couple and form C2 products.