Gamma and He ion radiolysis of copper oxides

Two copper oxides, cuprous and cupric oxide, were characterized using a variety of surface techniques including scanning electron microscopy, temperature-programmed desorption, diffuse reflectance infrared Fourier transform spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to analyze changes in the oxide surface following irradiation with γ-rays and 5 MeV 4He ions. The radiation chemical yield for molecular hydrogen was also measured for copper oxide powders with adsorbed water as well as with slurries containing various amounts of water. The yield of hydrogen was found to be slightly greater than the yield expected for bulk water radiolysis, indicating some small radiation chemical effect of the oxide surface on water. X-ray photoelectron spectroscopy indicated that the amount of OH groups present on the cuprous oxide surface decreased as a result of the irradiation while the cupric oxide surface had an increase in OH groups on the surface. This result suggests that the mechanism for the formation of H2 differs based on the surface composition and structure of the oxide.