Investigation of photocatalytic properties of pure and Ln(La3+, Eu3+, Ce3+) - modified ZnO powders synthesized by thermal method

Simple and fast thermal method is used to synthesize ZnO and Ln-modified (La3+, Eu3+, Ce3+) ZnO powders. Nanocrystalline photocatalysts with 2.0 mol% concentration are annealed at 100 degrees C for 1h. The pure and doped powders are characterized by a variety of characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM). The photocatalytic action of the mixtures is tested in photocatalytic oxidation of ethylene as model air pollutant (5000 ppm feed concentration) in gas-phase flat-plate continuous flow photocatalytic reactor at maximum ethylene contact time of 4 min and optimal relative humidity 30%. The powder-form samples are suspended in water and after sonication (24 kHz) to disintegrate agglomerates the slurry was deposited by the capillary method on TLC sheets (Merck) to obtain 1 mg/cm(2) loading. The photoactivity testing was carried out using UV-A and UV-C illumination (0.014 W/cm(2)). Sample 3 (Ce3+-doped)/ZnO was superior to pure ZnO. It gave the highest conversion degrees both under UV-A and UV-C illumination, whereupon the latter yielded superior performance. There was no activity under visible light illumination due to the wide band gap.