The electroreduction of CO2 for selective synthesis of different products (e.g., formate, CO, methanol, hydrocarbons) is one of the most investigated reactions at present and involves testing a large number and variety of catalysts. However, the vast majority of experimental electrocatalysis studies use conventional one-sample-at-a-time methods (e.g., linear and/or cyclic voltammetry on static and/or rotating individual electrodes) without providing spatially resolved catalytic activity information. Herein, we lay some of the groundwork that is necessary for the application of the scanning electrochemical microscopy (SECM) for experimental screening of catalyst arrays and simultaneous product detection. We demonstrate the potential of this method for electrocatalytic assessment of CO2 reduction to formate (CO2RF) catalyst arrays. One of the most promising catalysts for CO2RF is Sn/SnO2. Therefore, we studied an array consisting of three different Sn/SnOx catalysts: two surfaces prepared by electroreduction at either −1.25 V or −3 V vs. Ag/AgCl, and the unreduced, native, surface. Using simultaneous SECM scans of the array with fast scan (1 V s −1) cyclic voltammetry detection of the products (HCOO  , CO and H2) at the Pt ultramicroelectrode (UME) tip, we were able to consistently distinguish the electrocatalytic activities of these three compositionally (i.e., Sn, SnO, SnO2 ratio) and morphologically (i.e., from smooth surface to nanoparticles) different catalyst surfaces. Further extension and validation of this technique for larger catalyst arrays and matrices coupled with machine learning based processing of large data sets, could greatly accelerate the CO2 electroreduction catalyst discovery and process development. 2