P-061

Birute Serapinienė

birute.serapiniene@ftmc.lt

Algirdas Selskis, Evaldas Naujalis, Jurga Juodkazytė, Rimantas Ramanauskas

Centre for Physical Sciences and Technology (FTMC), Vilnius, Lithuania

Electrochemical Reduction of CO2 on Cu Nanofoam Electrode

The catalytic activity of the metal is highly sensitive to electrolysis conditions, including surface structure, morphology, and real surface area (Sr). Simple polycrystalline Cu electrodes have a rather small Sr and therefore their efficiency is low. Meanwhile, the selectivity and activity of Cu can be optimized by adjusting the surface roughness, the size, shape and interparticle distance of the Cu crystallites as well as the selection of the single crystal facets of the metal electrode. The ability of Cu nanostructures to convert CO2 into useful hydrocarbons such as ethylene or ethane (C2+) is also of great interest.

A three-dimensional nano-modified Cu electrodes or foams are characterized by a substantial number of interconnected and unconnected pores and therefore with high values of Sr. These samples were electrodeposited from acidic solutions that varied in different proportions of H2SO4 and CuSO4, as well as the presence of Cl- ions additives. The samples were analyzed for their structural features by SEM, while their catalytic activity was evaluated by voltammetry studies and the distribution of facets was assessed by Pb UPD measurements. Gaseous CO2 reduction products were quantified by gas chromatography.

Cu foam electrodes with roughness factors varying between 800 and 2100 were electrodeposited and characterized, and the results obtained allowed the determination of an optimal Sr value to optimize C2+ product selectivity. However, it was found that electrode roughness is not the only important parameter, since morphological features such as pore size and shape strongly influence the product distribution. The experimental conditions were determined when the Cu foam catalyst exhibits partial or complete CH4 suppression with the increase in C2+ product selectivity. The obtained results indicate that C2+ type product formation predominates over C1 when pore width and depth on Cu electrode were narrowed and increased, respectively. Our results established that the selectivity for C2 hydrocarbons as the main product can be tuned by changing the degree of branching in dendrite microstructures. The following morphological factors as preferential faceting can also lead to changes in CO2 reduction selectivity due to surface structure effects.