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 CO2 (CO2RR) on Cu, extending the concept of interphases to CO2 conversion. Investigating organic modifications on CuOx, 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 CO2RR experiments with 180 molecular modifiers identify functional groups affecting selectivity for ethanol and multi-carbon (C2+) products. We find that these modifiers consistently produce metal-organic interphases on the Cu or CuOx surface. These interphases modulate Cu coordination, CO2RR intermediates, and interfacial water configuration, significantly improving electrocatalytic performance. Testing across 11 CuOx-based catalysts validates this approach, culminating in the development of two electrocatalysts that achieve ~80% faradaic efficiency for C2+ products with ethanol partial current densities up to 328 and 507 mA cm−2. This study highlights the pivotal role of interphases in CO2RR, advancing CO2 conversion technologies.