MgO-TiO2 mixed oxide nanoparticles: Comparison of flame synthesis versus aerogel method; characterization, and photocatalytic activities

Titanium dioxide (TiO2) and mixed oxides, i.e., mixtures of magnesium oxide and titanium dioxide (MgO-TiO2) with different ratios were synthesized by two methods-flame synthesis and aerogel, for comparison of their properties. The samples were characterized by powder x-ray diffraction (pXRD), energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmet-Teller method of surface area measurements, ultraviolet-visible spectroscopy (UV-vis), and transition electron microscopic analysis. The pXRD patterns of different mixed oxides with different mole ratios revealed that there were formations of different compositions and phases. These mixed oxides were also used as photocatalysts in the UV-vis light to oxidize acetaldehyde, and carbon dioxide (CO2) was measured as a product. The mixed oxides with low content of MgO (similar to 1-2 mol%) were found to be more UV-active photocatalysts for the degradation of acetaldehyde than the degradation by Degussa P25 and as-synthesized TiO2, the highest by the MgO-TiO2 mixed oxides of 1: 50 ratio when comparisons were carried out among the samples prepared by the same method. Furthermore, the mixed oxides prepared by the aerogel method were found to be superior photocatalysts compared with the mixed oxides of equal ratio prepared by flame synthesis. This effect of insulator, MgO, on the photocatalytic activity of semiconductor, TiO2, was found to be interesting and can be applied for other applications as environmentally friendly materials.