Keeping sight of copper in single-atom catalysts for electrochemical carbon dioxide reduction

Carbon dioxide can be electrochemically converted into valuable multi-carbon products using Cu-based single-atom catalysts. However, transient cluster formation, which is undetectable using ex-situ techniques, may be responsible for C2+ products. Here we discuss these observations to highlight the need for operando characterisation when defining active sites. Cu-based single atom catalysts can convert CO2 into multi-carbon products, however, the assignment of active sites needs great caution. In this comment, the authors discuss the transient Cu cluster formation as active sites and emphasise the need for operando characterisation in mechanistic study.