Preparation Of Bismuth-based Composite Thin Films And Their Photocatalytic Properties Based On The Interface Charge Transfer Principle

Semiconductor photocatalysis technology is a promising environmental remediation technology which can be used to treat the inorganic or organic pollutants in the environment. Bismuth based semiconductor photocatalysts have been attached much attention for their outstanding optical and electrical properties and the controllable microstructures. However, easy recombination of photo generated electrons and holes results to the low photocatalytic effeciency, limiting their practical applications. Based on the principle of the interfacial charge transfer which can suppres the recombination of photo generated carriers and improve the photocatalytic activity, we designed to use Cu ions to enrich the photo induced electrons of Bi2O3, thus the recombination of photo generated carriers were restrained. The Cu Bi2O3 and mesoporous Si O2/Cu Bi2O3 transparent films were prepared, hoped to have antifogging and antifouling abilities under dark or weak light conditions. Using Bi2O3 as the source of bismuth, the g C3N4/Bi2O2CO3 and g C3N4/Bi OCl composite films were in situ prepared by a simple heat treatement method. The photocatalytic properties of the films were evaluated and the photocatalytic mechanisms were discussed. These results provided the possibility for developing novel nanocomposites as efficient photocatalysts.The Cu Bi2O3 and mesoporous Si O2/Cu Bi2O3 films were prepared by a simple sol gel/spin coating or dip coating method. The photocatalytic activity and self cleaning property of the films were estimated for the degradation of methyl orange(MO) wastewater and the removal of the stearic acid on the film surfaces. All the film samples keep a high tranparency and colourless. The results showed that the surface Cu species can enrich the photo induced electrons effectively and restrain the recombination of photo induced carriers, thus the photocatalytic activity of films were improved. However, the inner Cu species may become the photo induced carriers recombination centers and supress the photocatalytic activity. The mesoporous Si O2/Cu Bi2O3 films showed superhydrophilicity and antifogging property in dark. This is owe to the surface mesoporous structure provide the space locus for the formation of Si OH.With Bi2O3 as the basic unit, the g C3N4/Bi2O2CO3 and g C3N4/Bi OCl composite films were in situ prepared by using different g C3N4 precursors. The samples were characterized by XRD, SEM, TEM, UV Vis, XPS and fluorescence spectra analyses. The results showed that the composites materials have good visible light response and the two components contact closely in the materials. Photocatalytic experiment results showed that the composite films showed higher activity than the single semiconductor photocatalyst. Due to the closely contacted semiconductor composite materials and good matching band positions, the photo induced carriers were separated effectively and the activities of the composite photocatalysts were improved. In addition, the band structure of the semiconductor can be affected by the micromorphology structure, thus affect the optical performance of the semiconductor. This provides possibilities for developing novel nanocomposites as efficient visible light responsive photocatalysts.