Study On Preparation And Photocatalytic Properties Of Some Semiconductor Photocatalysts

The energy crisis and environmental pollution restrict the sustainable development of human society. How to resolve these two difficult problems is the attention and research focus of researchers in recent years. Semiconductor photocatalytic technology which is based on the solar energy transform into chemical energy not only can utilize sunlight for splitting water into hydrogen and oxygen to provide a clean energy, but also can catalytic degradation of organic pollutant to solve the environmental pollution problem. Furthermore, the photocatalytic technology exhibit a lot of advantages such as just needs a mild reaction condition, the photocatalytic process will not produce secondary pollution and the catalysts are easy to get. Therefore, semiconductor photocatalytic technology is expected to become an effective way to solve the problems of energy and environment.The key to realize industrialization application using semiconductor photocatalytic technology is development of wide spectral response photocatalytic materials. The precondition of improving the utilization ratio of solar energy is the absorption spectra of photocatalytic materials match with the solar spectrum. A high photocatalytic activity makes the applications of photocatalytic materials possible. Recently, both of developing high effective visible-light photocatalysts and improving the quantum efficiency have become important issues in the field of photocatalytic. Though many studies about modifying traditional photocatalyst or developing new photocatalyst to improve the solar spectrum response range and photocatalytic effect have been reported, there are lots of unknowns in photocatalytic system such as new material systems and the relationship between the structure and catalytic performance. In order to expand the scope of photocatalytic materials and complete the interrelation between materials structure and properties, this paper mainly studied the following aspects:1) A general and facile one-pot template-free hydrothermal strategy has been developed to synthesize various metal oxides (TiO2, SnO2and α-Fe2O3) hollow structure. The formation of hollow structure involves a trifluoroacetic acid assisted Ostwald ripening process. Photocatalytic activities of the as-prepared TiO2product are evaluated by the photodegradation of Rhodamine B and the samples exhibit higher photocatalytic activity than Degussa P25. In addition, electrochemical measurements demonstrate that all of the as-prepared metal oxides hollow spheres have the potential applications in lithium-ion battery.2) A simple and facile hydrothermal method for synthesis of hierarchical a-GaOOH architectures has been designed. The build approach of a-GaOOH hierarchical architectures have been discussed. Ionic liquids have played a key role on the formation of the hierarchical structures. On the one hand, it can offer enough OH-to accelerate hydrolysis of Ga3+and form precipitation. On the other hand, imidazolium cation in ionic liquids could be selectively adsorbed on crystal planes of a-GaOOH and assisted to prompt the formation of hierarchical structures by electrostatic attraction. After calcining the precursor in air, α-GaOOH can be then converted to mesoporous a-Ga2O3hierarchical structures by thermal decomposition while preserving the same morphology via a topologic process. Furthermore, the as-prepared mesoporous a-Ga2O3hierarchical structures display good photocatalytic activity.3) N-doped TiO2nanocrystals with dominant{001} facets have been designed and synthesized. In the first step, pure TiO2nanocrystals with dominant{001} facets have been fabricated using a hydrothermal method. After calcining the samples processed by ethylenediamine under vacuum at different temperatures, N-doped TiO2nanocrystals with dominant{001} facets have been prepared successfully. Analyzed by XPS and BET, the composition of the photocatalysts has been investigated. Furthermore, the as-prepared N-doped photocatalysts showed excellent photocatalytic activities under visible light irradiation.4) Two kinds of vanadate materials have been synthesized and explored, i) Novel a-Ag3VO4nanostructures have been successfully synthesized via a facile and repeatable precipitation method by using n-butylamine as precipitant and complexing agent. By adjusting the amount of n-butylamine, a-Ag3VO4nanostars and nanoflowers have been prepared. Photocatalytic property tests for decomposition of RhB demonstrate that the as-prepared nanostructures have enhanced photocatalytic activity. ii) BiVO4dendritic structure has been synthesized using a simple hydrothermal method and the morphology of the samples has been investigated. Based on the experimental results, it is considered that NH4F played a key role in the formation of dendritic structure. The possible growth mechanism has been proposed. The products exhibit good visible light photocatalytic activity and excellent stability.