Scanning electrochemical microscopy screening of CO 2 electroreduction activities and product selectivities of catalyst arrays.

The electroreduction of CO 2 is one of the most investigated reactions and involves testing a large number and variety of catalysts. The majority of experimental electrocatalysis studies use conventional one-sample-at-a-time methods without providing spatially resolved catalytic activity information. Herein, we present the application of scanning electrochemical microscopy (SECM) for simultaneous screening of different catalysts forming an array. We demonstrate the potential of this method for electrocatalytic assessment of an array consisting of three Sn/SnO x catalysts for CO 2 reduction to formate (CO2RF). Simultaneous SECM scans with fast scan (1 V s -1 ) cyclic voltammetry detection of products (HCOO - , CO and H 2 ) at the Pt ultramicroelectrode tip were performed. We were able to consistently distinguish the electrocatalytic activities of the three compositionally and morphologically different Sn/SnO x catalysts. Further development of this technique for larger catalyst arrays and matrices coupled with machine learning based algorithms could greatly accelerate the CO 2 electroreduction catalyst discovery.