Effect of Current Density on Product Distribution for the Electrocatalytic Reduction of CO2.

The effect of current density on product distribution and yield in the electrochemical reduction of carbon dioxide was studied by processing low-cost and non-critical raw materials. Specifically, the electrodes were prepared by depositing copper (Cu) nanoparticles on functionalized carbon nanotubes (CNTs), then assembled with a gas diffusion layer and a proton exchange membrane. The as-prepared electrodes were fully characterized by different advanced techniques to study their morphological and structural characteristics, as well as their electrochemical properties. Finally, the electrodes were tested in the process of CO₂ electroreduction by using a compact electrochemical device, designed on purpose to minimize overpotential phenomena. The tests were carried out under a continuous flow of pure CO₂ in 0.1 M KHCO₃ as the electrolyte, applying different voltages (from -0.5 to -1.7 V vs. Ag/AgCl) in order to obtain different current densities (from 0.1 to 2.3 mA cm^-2, respectively). Furthermore, tests under industrial relevant conditions (high current density) were performed by providing directly 10 mA cm^-2 to the working electrode. Results showed that current density strongly influences the product distribution, with formic acid and CO being the main products at high current density, while products like methanol, ethanol, isopropanol, acetic acid, and oxalic acid were formed at lower applied potential. [ABSTRACT FROM AUTHOR]