Electrocatalytic conversion of carbon dioxide to alcohols using composites of nano-Cu, Ag, and graphite electrodes

Vehicle emissions of carbon dioxide significantly contribute to greenhouse gases. Recycling this CO₂ into valuable hydrocarbon products enhances vehicle mileage while reducing environmental impact, adding value to fuel consumption. This research aims to utilize the electrochemical method for conversion of CO₂ to alcohols using nano-copper (Cu), silver (Ag), graphite (C), and their composites. Pure graphite, nano-copper, silver, and their composites were evaluated for the performance in CO₂ reduction. The working solution was 0.1 M potassium bicarbonate (KHCO₃) saturated with CO₂ in H-type cell. The produced alcohols were continuously monitored to assess the efficiency of the electrochemical conversion process. Nano-copper electrodes showed high Faradaic efficiencies for methanol (~ 100%), ethanol (~ 100%), and hydrogen reduction. The Cu/graphite composites revealed enhanced performance, benefiting from the synergy between the CO₂ adsorption properties of graphite and the catalytic activity of copper. Mixed Cu-Ag systems, on the other hand, showed distinct electrochemical behavior through the CO-pathway reaction steps. The electrodes of graphite, copper, and their composites were characterized for their surface morphologies, crystallinity, and functional groups. X-ray diffraction (XRD) confirmed the presence of copper phases in the E₂₁Cu₇₉C composite, and scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses provided an uneven amorphous surface with major -OH groups that can enhance the adsorption of CO₂ to these electrodes. The addition of copper to graphite in E₂₁Cu₇₉C electrode indicated a positive increase of 4% in reduction potential from pure graphite. Pure graphite electrode provided a current density of 27.8 mA/cm², whereas Cu/graphite (E₂₁Cu₇₉C) demonstrated an increase of 12%. This study highlights the importance of electrode composition in optimizing CO₂ electro-reduction, offering insights into the development of more efficient catalysts for the sustainable production of alcohols from CO₂.