Nanoparticles based on copper deposited on carbon spheres. Preparation, characterization and application for CO2 photo-electrochemical reduction

In this study, we have examined the performance of copper nanoparticles deposited on carbon spheres with a mass weigh of 10 wt% (labeled 10Cu-CSs) via photo-electrochemical reduction of carbon dioxide (CO2). The carbon spheres (CSs) were prepared by a chemical vapor deposition method and 10Cu-CSs was made via a homogeneous deposition precipitation method. The materials were characterized by different physico-chemical techniques such as X-ray diffraction (XRD), Raman, Fourier transform infrared (FTIR) and diffuse reflectance (DR) spectroscopy, electrical conductivity and photo-electrochemical studies. The 10Cu-CSs material was studied for the photo-electrochemical reduction of CO2 under visible light illumination. The synthesized material exhibited a single phase monoclinic structure of CuO deposited on CSs as confirmed by XRD, Raman and FTIR spectroscopies results. The semi-conductor property was established by electrical conductivity, and the activation energy obtained was ca. 0.04 eV. The UV-visible absorption spectrum showed a direct band gap transition with gap energy of 1.22 eV. The material synthesized was a cathode semi-conductor with p-type conductivity. The deposition of copper nanoparticles enhanced the CO2 photo-conversion to formic acid under the reaction conditions. In particular, 10Cu-CSs demonstrated gave formic acid, which was at a higher potential than standard redox potentials of copper. Furthermore, the photo-electrochemical characterization showed that the deposition of the copper onto CSs used as electrode effectively generated photo-induced electron/hole pairs under visible light irradiation leading an enhancement of photo-reduction under visible light in a NaHCO3 electrolyte.