XPS investigation on the surface of ZnO photocatalytic films obtained by polymer modified spray pyrolysis

Photocatalytically active ZnO nanosized films were deposited by polymer modified spray pyrolysis method. The influence of the polymers and the type of zinc precursor on the chemical composition, surface morphologies and the photocatalytic properties towards Malachite Green dye degradation were investigated. The amount of oxygen in the lattice (O L ) and oxygen total (O T ) as well as the atomic ratio of Zn/O T were evaluated by means of X-ray Photoelectron Spectroscopy (XPS). The ZnO films are non-stoichiometric. The addition of polymers to both zinc salt solutions does not change significantly the oxygen concentration in the films. After photocatalytic test the ratio O L /O T decreases, showing that the amount of adsorbed hydroxyl groups is increased. The films obtained from zinc acetate possess higher photocatalytic activity than those, obtained from zinc nitrate. The highest efficiency is achieved with the films obtained from zinc acetate with ethylcellulose addition

Dependence of the textural properties and surface species of ZnO photocatalytic materials on the type of precipitating agent used in the hydrothermal synthesis

Three different precipitating agents (NaOH, NH4(H)CO3 and CO(NH2)2) have been applied for the hydrothermal synthesis of ZnO powder materials, aiming at obtaining various types of porosity and surface species on ZnO. The synthesis procedures were carried out in the presence and in the absence of tri-block copolymer Pluronic (P123, EO20PO70EO20). These materials were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM)–energy-dispersive X-ray spectroscopy (EDX), BET method and TG–differential thermal analysis (DTA) method, and their photocatalytic activities were tested in the removal of azo dye Reactive Black 5 (RB5). The urea precipitant yields spongy-like surface forms and the greatest share of mesopores. It has the highest specific surface area, the highest degree of crystallinity of wurtzite ZnO phase and largest content of surface OH groups in comparison with the other two precipitants. The zinc hydroxycarbonate intermediate phase is missing in the case of NaOH as a precipitating agent; therefore, it manifests poorer textural characteristics. The morphology of P123-modified sample is different and consists of needle-shaped particles. The urea-precipitated samples display superior performance in the photocatalytic oxidation reaction, compared with the other precipitated samples. The other two precipitating agents are inferior in regard to their photocatalytic activity due to a greater share of micropores (not well-illuminated inner surface) and different surface morphologies