PC#3 still manages to fully separate the elements according to their major product, although the distance between CO-and HCOOH-producing metals is smaller. As we use principal components rather than individual descriptors, this plot does not directly tell us which of the features in the dataset are the most important for understanding CO 2 RR selectivity. We cannot translate our PCA statistical insight directly to chemical insight in the form of a reaction mechanism, although our results do give us additional mechanistic insight.