Synthesis and Characterization of Annealed ZnO and Cu5%-doped ZnO Nanoparticles and Their Photocatalytic Applications

Abstract

In this study, mesoporous ZnO (pure) and Zn0.95Cu0.05O were prepared using a simple solgel method in the presence of 2.3-dihydroxysuccinic acid as catalyst. The powders obtained were annealed under air in the temperature range: 250 - 550C. The ratio of Cu:Zn obtained from energy dispersive x-ray (EDX) was (4.8%). X-ray diffraction (XRD) analysis indicated that the wurtzite structure was maintained for all samples and copper was successfully doped into ZnO at low TC with the formation of monoclinic CuO at higher TC. Surface area analysis, confirmed that mesoporous ZnO with different surface area in the 109.7 to 7.48m2/g range and mean diameter of 16.03 to 25.03 nm after annealing at different temperature. For Zn0.95Cu0.05O, the crystallite size increased with the annealing temperature from 15.86 to 24.24 nm and the surface area was in the range 35.1 to 8.66 m2/g. The isotherms obtained for all specimens were type IV with a hysteresis type H3, confirming the mesoporous behavior of the catalysts. The vibration stretching band of pure ZnO was shifted to lower wavenumber due to annealing from 250 -550C. All the prepared catalysts showed two emission regions: a sharp peak in the ultraviolet region and another broad peak in the visible region. The photocatalytic activity was achieved by adsorption kinetics and the degradation of 300 mg/L malachite green (MG) aqueous solution under UV irradiation. The findings showed that increased annealing of Cu5% doped ZnO with CuO on the surface resulted in highly improved photocatalytic activity.