UC Berkeley

Electrochemical CO2 reduction provides a promising route to the sustainable generation of valuable chemicals and fuels. Tandem catalysts enable sequential CO2-to-CO and CO-to-multicarbon (C2+) product conversions on complementary active sites, to produce high C2+ Faradaic efficiency (FE). Unfortunately, previous tandem catalysts exhibit poor management of CO intermediates, which diminishes C2+ FE. Here, we design segmented gas-diffusion electrodes (s-GDEs) in which a CO-selective catalyst layer (CL) segment at the inlet prolongs CO residence time in the subsequent C2+-selective segment, enhancing conversion. This phenomenon enables increases in both the CO utilization and C2+ current density for a Cu/Ag s-GDE compared to pure Cu, by increasing the *CO coverage within the Cu CL. Lastly, we develop a Cu/Fe-N-C s-GDE with 90% C2+ FE at C2+ partial current density (jC2+) exceeding 1 A cm⁻². These results prove the importance of transport and establish design principles to improve C2+ FE and jC2+ in tandem CO2 reduction. [Figure not available: see fulltext.]