Observation of metal-organic interphase in Cu-based electrochemical CO2-to-ethanol conversion

Interphases are critical in electrochemical systems, influencing performance by controlling ion transport and stability. This study explores a metal-organic interphase in the electrocatalytic reduction of CO 2 (CO 2 RR) on Cu, extending the concept of interphases to CO 2 conversion. Investigating organic modifications on CuO x , we discover metal-organic interphases over 10 nm thick in highly ethanol-selective systems, contrary to the expected monolayer adsorption. Using an automated platform, 1080 CO 2 RR experiments with 180 molecular modifiers identify functional groups affecting selectivity for ethanol and multi-carbon (C 2+ ) products. We find that these modifiers consistently produce metal-organic interphases on the Cu or CuO x surface. These interphases modulate Cu coordination, CO 2 RR intermediates, and interfacial water configuration, significantly improving electrocatalytic performance. Testing across 11 CuO x -based catalysts validates this approach, culminating in the development of two electrocatalysts that achieve ~80% faradaic efficiency for C 2+ products with ethanol partial current densities up to 328 and 507 mA cm −2 . This study highlights the pivotal role of interphases in CO 2 RR, advancing CO 2 conversion technologies.