Research Information System
JOURNAL OF THE IRANIAN CHEMICAL SOCIETY, vol.23, no.1, 2026 (SCI-Expanded, Scopus)
The delafossite CuAlO2 was prepared by sol-gel method and X-ray diffraction of the oxide fired at 1100 degrees C is characteristic of a single phase, crystallizing in a rhombohedral structure (R (3) over barm) with a crystallite size of 58 (+/- 2 nm). A grain size of 0.55 mu m and a zeta potential (- 8 mV) were determined by zetammetry. A direct optical gap of 1.83 eV, obtained from the diffuse reflectance, is due to a lifting of the degeneracy of Cu+: d-d in a linear crystal field. An additional transition at 3.69 eV is due to charge transfer (O-2(-): 2p -> Cu+: 4s). CuAlO2 exhibits p-type conduction behavior with a lattice polaron hopping between Cu2+/+ states due to the intercalation of O2- between the reticular planes (0 0 n). The electrical conductivity varies linearly with the reciprocal temperature, indicating semiconductor character which obeys to an exponential law: sigma = sigma(o) exp(- 0.26 eV/kT) over the range (300-500 K). The photoelectrochemical study was undertaken in Na2SO4 electrolyte (0.1 mol dm(-3)); a flat band of 0.20 V-SCE and a hole concentration of 1.13 x 10(18) cm(-3) were determined from the capacitance-potential graph. Electrochemical Impedance Spectroscopy (EIS) shows a semicircle centered on the real axis, indicating pure capacitive behavior. The inclined line at low frequencies (35 degrees) indicates ionic diffusion in the crystal lattice. As application, the decolorization of methylene blue (MB, 92%) within 70 min under optimal conditions by hydroxyl (HO & sdot;) and superoxide (O-2(& sdot;-)). "Photocatalysis/ultrasound (USW)" is superior to both photocatalytic oxidation (CuAlO2/Sunlight) and CuAlO2/USW. A high chemical oxygen demand (COD) is obtained at low frequency ultrasonic waves (60 kHz) corresponds to high mineralization with {USW/sunlight/CuAlO2}. The kinetics of these simultaneous processes follows a pseudo-prime model with a rate constant of 1.96 x 10(-2) min(-1) (t(1/2) = 35 min). The sono-photo-catalytic activity, reusability and stability of CuAlO2 were found to be excellent.