Copper and copper-based catalysts can electrochemically convert CO₂ into ethylene and higher alcohols, among other products, at room temperature and pressure. This approach may be suitable for the production of high-value compounds. However, such a promising reaction is heavily burdened by the instability of copper during CO₂ reduction. To date, non-copper catalysts have also failed to supplant the activity and selectivity of copper, leaving CO₂-to-C₂ electrolysis in the balance. In this Perspective, we discuss copper catalyst instability from both the atomistic and the microstructure viewpoint. We motivate that increased fundamental understanding, material design and operational approaches, along with increased reporting of failure mechanisms, will contribute to overcoming the barriers to multi-year operation. Our narrative focuses on the copper catalyst reconstruction occurring during CO₂ reduction as one of the major causes inducing loss of C₂ activity. We conclude with a rational path forward towards longer operations of CO₂-to-C₂ electrolysis.

Correction to: Nature Reviews Materialshttps://doi.org/10.1038/s41578-025-00815-0, published online 16 June 2025. In the version of the article initially published, in Fig. 4b, the labels “Gas-diffusion layer” and “Copper catalyst layer” were switched and have now been amended so that the upper layer is labelled as the “Copper catalyst layer” and the lower layer is the “Gas-diffusion layer”. This correction has been made to the HTML and PDF versions of the article.