CO2 valorization through nanostructured Cu-based electrocatalysts

The widespread use of fossil fuels has led to the release of significant amounts of carbon dioxide CO2 in the atmosphere, contributing to global warming. One potential solution to address this issue is CO2 electroreduction, a process that converts CO2 into valuable carbon-based products. Furthermore, by harnessing renewable energy sources and utilizing fuels produced through CO2 electroreduction, it is possible to establish a carbon-neutral CO2 cycle. Catalysts are pivotal in this process as they reduce the activation energy barrier of CO2, which is inherently a stable and fully oxidized linear molecule. In this research, we have investigated several types of catalysts for CO2 electrochemical reduction: Cu nanowires supported on Carbon Vulcan and Cu and Ag nanoparticles synthesized through radiolysis on a TiO2 support. The main objective of this project is to assess the catalysts' activity and selectivity in producing valuable CO2 electroreduction products with high energy density and market value, addressing both environmental and energy-related challenges. To characterize the catalysts, we conducted various analyses, including UV-Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). We also evaluated the electrochemical properties using cyclic voltammetry and chrono amperometry. Reduced products in the gas phase were analyzed by the micro-GC. The resulting chromatograms showed that the samples synthesized on TiO2 analyzed in the dark appeared to produce only H2 and, therefore, exhibited no catalytic activity towards CO2. However, when the CO2 reduction reaction was performed under solar light irradiation, there was an increased production of H2and the generation of hydrocarbons in small concentrations. In contrast, the Cu NWs on the Carbon Vulcan support, after the CO2 reduction reaction, showed the production of H2, CO, and an unidentified hydrocarbon detected by the micro-GC. The gaseous phase resulting from the CO2 reduction by CU NWs was further analyzed using GC-MS, which revealed the production of acetic acid. The variation in catalytic activity towards CO2 among the different samples can be attributed to the higher electrochemical activity exhibited by Cu NWs on Carbon Vulcan compared to the nanoparticles synthesized on TiO2.