Co‐Cu Materials Library Screening for Discovering Electrocatalysts for the Co‐Reduction of CO ₂ and Nitrate to Urea

The electrocatalytic synthesis of urea by coreduction of NO 3 − and CO 2 provides the basis to replace the energy‐intensive Bosch–Meiser process; however, such systems are inherently limited by competing reactions and urea selectivity. Scanning electrochemical cell microscopy (SECCM) with a cosputtered Co‐Cu alloy thin‐film materials library is used for the high‐throughput investigation of element composition‐dependent electrochemical activity for the coreduction of CO 2 and NO 3 − to urea. A NO 3 − containing electrolyte is provided in the SECCM capillary while CO 2 is offered through the gas phase. Comparison of linear sweep voltammograms in presence and absence of CO 2 is the basis for finding Co‐Cu compositions which exhibit an increased overpotential for NO 3 − reduction for matching the potentials for CO 2 reduction, thus allowing the presence of the intermediates of both reactions in close vicinity at the catalytic sites. The most promising Co‐Cu element ratio for urea synthesis is synthesized as a powder catalyst and investigated in a model flow‐through electrolyzer concerning urea synthesis. These findings provide guidance for the rational design of Co‐Cu (Co x Cu 100−x ) catalysts, the optimization and the identification of optimal working potentials as well as electrolyte compositions to facilitate CN coupling to urea with minimal loss caused by competing reactions.