For the strongly CO-adsorbing metals, CO desorption is always rate-limiting, and the surface is fully covered with CO (cf. Supplementary Fig. ). According to the new activity volcano, Pd is a catalyst with impressively high activity comparable to Ag. Pd is indeed also experimentally known to produce CO, albeit it is rarely discussed as a promising CO 2 RR catalyst due to the prevailing hydrogen evolution reaction (HER). To visualize the regions of high HER rate, we correlated the hydrogen adsorption energy (without accounting for the field interaction which is a small effect 32 ) with the two descriptors and found a high R 2 = 0.90. This correlation originates mostly from the correlation with the CO adsorption energy (R 2 = 0.87), leading to almost horizontal isosurfaces of the H adsorption energy in Fig. , with the stronger binding CO metals showing increased HER activity. The high CO coverage, however, can to some degree suppress HER by poisoning active sites. Therefore, if means to suppress HER can be employed and improved, such electrocatalysts might become highly promising candidates. Finally, we also mention that due to saturation of the CO coverage (cf. Supplementary Fig. ), the CO formation rate is independent of pH also in this region, suggesting again a minor role of the pH in enhancing the CO production rate (cf. also Supplementary Fig. showing the pH effect on the activity volcano).