Synthesis mechanism of cuprous oxide nanoparticles by atmospheric-pressure plasma electrolysis

The synthesis mechanism of cuprous oxide (Cu₂O) nanoparticles by atmospheric-pressure plasma electrolysis was investigated experimentally. In the plasma electrolysis system, a helium plasma in contact with an NaCl electrolyte was used as the cathode, while a copper plate which was partly immersed into the electrolyte was used as the counter electrode. X-ray powder diffraction, field-emission scanning electron microscopy, and transmission electron microscopy were used for characterizing the synthesized products. The results indicate that the Cl⁻ concentration and the pH value of the electrolyte dominate the synthesis of Cu₂O nanoparticles. The reaction between CuCl 2 − produced via the anodic dissolution of Cu and OH⁻ produced by plasma irradiation is responsible for the formation of Cu₂O. The comparison between the plasma and conventional electrolysis has also been carried out, since the anodic dissolution of the Cu plate and the production of OH⁻ are also available in the conventional electrolysis. As a result, we also observed the synthesis of Cu₂O nanoparticles by the conventional electrolysis. However, we observed the differences between the plasma and conventional electrolysis in the synthesis rate, the minimum NaCl concentration, and the size and the shape of synthesized nanoparticles.