Investigating aging processes and characterization of nanodispersed Cu-Al layered double hydroxides produced by non-equilibrium electrochemical oxidation

The present paper describes an investigation of aging processes and the characterization of nanodispersed materials prepared by non-equilibrium electrochemical oxidation of metals. X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) analyses, and the reflectance spectra investigation were used to characterize the electrolysis products aged naturally over time. The ageing of electrolysis products in the solution leads to the conversion of Cu2O-AlOOH into Cu-Al layered double hydroxides (Cu-Al-CO3-LDH) and Cu2(OH)2CO3 due to the Jahn-Teller effect. Long-term aging results in: (i) stability of phase composition but a slight increase of the interplanar spacing due to the sorption ability of the nanostructures in air; (ii) temperature decrease of Cu-Al-CO3-LDH decomposition from 135 to 121 degrees C due to the stability deterioration with further content increase of carbonate ions (DSC analysis) and decrease of hydroxide ions (FT-IR analysis); (iii) 2.5 times increase of the coherent scattering region (CSR) of all copper-containing compounds compared with short-term aging (40-50 nm vs. 15-20 nm); and (iv) no size change of the flower-like Cu-Al-CO3LDH and dramatical size decrease of nanodispersed particles of CuO and Cu2(OH)2CO3 because of deagglomeration. Conversion CuO/Al2O3 to Cu-Al-CO3-LDH makes a positive impact on photocatalytic activity of nanodispersed materials while it results in the increase the reflection coefficient.