Direct synthesis of TiO2 nanoparticles by using the solid-state precursor TiH2 powder in a thermal plasma reactor

We attempt the direct synthesis of TiO2 by using the solid state precursor TiH2 powder with oxygen in a thermal plasma reactor. Nanocrystalline titanium dioxide powder has been synthesized by using thermal plasma synthesis in a non-transferred arc thermal plasma reactor. The thermal plasma-synthesized powder product consists of nano-sized particles of anatase and rutile phases of titanium dioxide. Particle compositions were observed on collecting powder from different positions of the reactor and varying the amount of flow rate of reactive gases (O2). The characteristics of the powder such as particle size, size distribution and phases were analyzed using various techniques such as XRD, SEM, TEM, XPS, EDS and particle size analyzer. UV–visible reflection spectroscopy of the plasma-synthesized TiO2 powders showed the absorbance in the visible region leading to effective photocatalytic activity, which is clearly confirmed from the XPS analysis. XPS analysis reveals the presence of –OH bonds on the surface of nanoparticles, which is the significant evidence of better quality of powders in comparison to other methods. Also, we have investigated the phase transformation phenomenon of anatase to rutile. At 1000 °C, complete transformation of the anatase to rutile occurs. Powders prepared in this procedure are white in colour and their diameter varies from 10 nm to 150 nm. Average particle size distributes in the range of 20–50 nm. The unique property about the plasma-synthesized powders is high resistance to heat treatment, with enhanced photocatalytic activity.

Graphical abstractTiO2 nanoparticles were prepared by direct synthesis using the solid-state precursor TiH2 powder in a thermal plasma reactor. The particle size, effects of concentration of OH− on the photocatalytic properties and effect of heat treatment were investigated.Figure optionsDownload full-size imageDownload high-quality image (260 K)Download as PowerPoint slideHighlights► Direct synthesis of TiO2 nanoparticles in a thermal plasma reactor using TiH2 as solid-state precursor. ► Nanoparticles obtained having particle size 10–150 nm with average diameter 50 nm. ► Surface of the particles in plasma-synthesized TiO2 nano powders mostly contains the –OH bond which showed the absorbance in the visible region leading to effective photocatalytic activity. ► The unique quality about this process is that nanoparticles obtained were having high resistance to heat treatment.