However, a large part of the metals presented in the figures so far is not actually selectively forming CO during CO 2 RR, but rather formate, C 1 -or C 2 -products or even rather performing the HER. The construction of a kinetic model for all of these processes has been and others (Cu, In, Au, Ag, Sn, This suggests that the same descriptor pair that we suggest here might be again valid also to describe the activity for other products and thus also the selectivity trends. Indeed, the formation of C 2 products is limited by the field-driven coupling of two *CO intermediates which suggests the necessity of the PZC descriptor to explain selectivity trends. Finally, we record that if discovered descriptors would be useful also for the description of other product pathways, a plot of the experimentally revealed dominant product selectivity as a function of these descriptors should clearly separate into selectivity regions. In Fig. a) we show the experimentally determined dominant product of electrochemical CO 2 RR at -1.4 V vs. SHE and pH = 6.8 from experimental studies using planar electrodes.