Optimized Dendrite Copper Surface Enables Selective C 2+ Product Conversion from CO 2 Electroreduction

Electrosynthesis of valuable fuels like higher-order alcohols and olefins from CO 2 electroreduction is a promising strategy, but achieving high selectivity, particularly for ethylene and ethanol, remains a key challenge. This is largely due to the complex 12-electron reaction pathways and challenging hydrogen evolution. Copper (Cu) is a commanding electrocatalyst in this field due to its ability to uphold C-C bond formation. Existing research is focused on developing modified Cu catalysts, including oxide-derived, atomic, and vacancy-containing structures, to overcome selectivity limitations in CO 2 electroreduction. Dendritic copper (den-Cu) catalysts with high surface areas were synthesized on gas diffusion layer (GDL) electrodes by a galvanostatic electrochemical deposition method in KHCO 3 electrolyte. The deposition current and thickness were carefully optimized to maximize the production of valuable C 2+ products, specifically ethanol and ethylene from CO 2 electroreduction. The resulting dendritic-Cu nanostructured catalysts demonstrated excellent selectivity and activity, attaining a total C 2+ Faradaic efficiency (FE) of 76% with 176 mA/cm² current density while demonstrating a diminutive FE of 8% for H₂ at -2.8 V applied cell potential in a 5 cm 2 membrane electrode assembly (MEA) incorporating an anion exchange membrane. The den-Cu 25-1 electrode exhibited an elevated ethanol turnover frequency (TOF) of 2719 h⁻¹ and a partial current density (j partial ) of 70 mA/cm² at -2.8V due to its larger active surface area favoring CO₂ reduction reaction. Characterization techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and electrochemical analysis, were employed to understand the catalyst properties. Cooperative research will focus on elucidating the influence of the dendritic Cu surface on CO 2 -C 2+ reduction selectivity and activity.