In this work, four different 4 cm2-sized nanostructured Cu-based electrocatalysts have been designed by a one-step electrodeposition process of Cu metal on a three-dimensional carbonaceous membrane. One consisted of Cu0, and the other three were obtained by further simple oxidative treatments. Morphological, structural, and electrochemical investigations on the four materials were carried out by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, linear sweep voltammetry, and potential-controlled electrolysis. All the electrocatalysts showed promising catalytic activities toward CO2 electroreduction in liquid phase, with a remarkable selectivity toward acetic acid achieved when using the oxidized materials. In particular, the best electrocatalytic activity was observed for the Cu2O-Cu0 catalyst, working at a relatively low potential (-0.4 V vs RHE), which exhibited a stable and low current density of 0.46 mA cm-2 and a productivity of 308 μmol gcat-1 h-1. These results were attributed to the nanostructured morphology that is characterized by many void spaces and by a high surface area, which should guarantee a large number of CuI and Cu0 catalytic active sites. Moreover, kinetic analyses and preliminary studies about catalyst regeneration highlighted the stability of the best-performing catalyst.
Keywords: CO2 conversion; Cu-based electrocatalyst; acetic acid; electroreduction; gas diffusion layer; nanostructure.