Organic Thin Films Enable Retaining the Oxidation State of Copper Catalysts during CO 2 Electroreduction.

A key challenge in electrocatalysis remains controlling a catalyst's structural, chemical, and electrical properties under reaction conditions. While organic coatings showed promise for enhancing the selectivity and stability of catalysts for CO 2 electroreduction (CO 2 RR), their impact on the chemical state of underlying metal electrodes has remained unclear. In this study, we show that organic thin films on polycrystalline copper (Cu) enable retaining Cu + species at reducing potentials down to -1.0 V vs RHE, as evidenced by operando Raman and quasi in situ X-ray photoelectron spectroscopy. In situ electrochemical atomic force microscopy revealed the integrity of the porous organic film and nearly unaltered Cu electrode morphology. While the pristine thin film enhances the CO 2 -to-ethylene conversion, the addition of organic modifiers into electrolytes gives rise to improved CO 2 RR performance stability. Our findings showcase hybrid metal-organic systems as a versatile approach to control, beyond morphology and local environment, the oxidation states of catalysts and energy conversion materials.