Synthesis of ZnO-Al:TiO2 Materials and their Characterization as Photocatalyst Compounds

Abstract

Photocatalyst activity relates to the active surface area between pollutants and catalyst compounds. The insertion of Al atoms as a substantial defect in ZnO structures can reduce the particle size thus the active surface area increases. Another way to raise the photocatalytic activity of ZnO is by combination with other oxide materials such as TiO2 (Titanium dioxide). In this study, the ZnO-Al:TiO2 powder was successfully prepared via the sol-gel method using zinc acetate dihydrate as a precursor, 0.5wt% of aluminum nitrate nonahydrate as a dopant precursor, and TiO2 anatase. In order to understand the role of the combination of these two metal oxides, the concentration ratio of ZnO-Al and TiO2 was varied by 1:1 (ZAT) and 4:1 (ZA4T) under low (150°C) and high (450°C) temperature calcination. Photocatalytic testing was carried out using a 3.2 ppm methylene blue (MB) solution under UV-A lamp irradiation for 120 minutes. The high calcination temperature facilitates the growth of ZnO-Al. Besides that, the different ratio concentrations and calcination temperatures produce different defect states in each sample. The most optimum results in the photocatalytic activity performed by ZnO-Al:TiO2 150°C (ZAT 15) with degradation rate constant (k) of 0.033/min and efficiency of 97% for MB removal. The unexpected zinc vacancies defect is estimated produce at the samples in high-temperature calcination. This defect type can accelerate electron-hole pair recombination. In Addition, samples with high-temperature calcination were considered to have lower hydroxyl/oxygen bonds on the surface thus affecting the photocatalytic performance.