In the study, the catalytic edge reactivity on porous Zn electrode has successfully visualized through the electrochemical CO2 reduction to CO. It is well known that the activity of a CO2 reduction reaction catalyst depend on the type of material and surface nano-structure. Consequently, numerous researchers are interested in the relation between the catalyst activity and surface conditions such as morphology, oxidation state, and crystal orientation. However, it is difficult to explain the mechanisms of catalytic CO2 reduction and visualize the catalytic activity. Our results demonstrate, that this strategy not only improved the selective CO production, but also helped visualize the catalytic reactivity on the edge site via open-loop electric potential microscopy (OL-EPM). The obtained OL-EPM image strongly suggests that the edge site of porous Zn acts as an efficient reactive site in the CO2 electrochemical reduction reaction. (C) 2018 Elsevier Ltd. All rights reserved.