K.K. Akurati, A. Vital, F. Reifler, A. Ritter and T. Graule
photocatalysis, visible light, nanoparticles, flame spray, aerosol
Photocatalysis phenomenon has attracted considerable interest in recent years because of its usage in water purification, environmental cleaning, solar energy conversion and generation of alternative energy resources. To date, TiO2 has undoubtedly proven to be the most effective photocatalyst. However, owing to the large band gap of TiO2, it is not suitable for the usage as visible light active photocatalyst. Since photocatalysis is a surface phenomenon, less surface area of the large particles hinders the number of active sites where the photocatalytic reaction can take place. Hence there is a need to synthesize the visible light absorbing photocatalysts with high specific surface area. In the present study, flame spray pyrolysis has been employed to synthesize Ca-Bi-O and W-Bi-O nanoparticles. Influence of the process parameters (flow rate of the precursor solution, nature of the solvent and precursor) on the nanoparticle characteristics have been studied by nitrogen physisorption (measuring specific surface area), x-ray diffraction (phase composition), transmission electron microscopy (size, shape and morphology of the particles), whilst UV-vis diffuse reflectance spectroscopy analyzed with the Kubelka-Munk function has been used to study the visible light absorption of the photocatalyst and the optical band gaps. Rate of degradation of ethylene glycol, dodecanol, C17 alkane under visible light illumination (>400 nm) has been used as the measure of the photocatalytic activity (PCA) of the particles whose specific surface area ranges from 30 to 100 m2/g. Clear dependence of the specific surface area and crystallinity of the particles on the PCA has been observed which signifies the advantages of nanoparticles. Moreover, the ability of the synthesis of Ca-Bi-O and W-Bi-O nanoparticles by flame spray pyrolysis at high production rates has been shown.