Controllable Synthesis And Photocatalyitc Properties Of Zn_xCd_1-xS And Its Nanocomposites

Solar driven photocatalysts for H2-production from water splitting and degradation organic pollutants are seen as a viable strategy for solving energy crisis and environmental problems in 21 st century.Therefore, the reasonable design and synthesis of effective semiconductor photocatalytic materials with visible light res ponse has been becoming one of the hot research fields. As a typical group of semiconductors, â…¡-â…¥ semiconductor nanomaterials have attracted extensive investigation due to their unique optical, magnetic and electrical properties and the intriguing applied prospects in the semiconductor laser, solid light and solar cells, etc. Recently, Zn S, Cd S and Zn xCd1-x S have received significant attentions of reseatchers owing to their active and unique photocatalytic activity. It is well known that the photocatalytic activity of nanomaterials largely depends on the chemical composition, size, morphology of the photocatalysts.Thus, developing facile synthetic approaches to control over the particle size, morphology and chemical composition of the metal sulfides is highly desirable for both growth mechanism studies and their application.In this paper, a inexpensive and simple chemical bath deposition(CBD) procedure is presented for controllable synthesis ZnxCd1-xS,ZnxCd1-xS/Ti O2 and ZnxCd1-xS/Ce O2 nanostructures, and the influence of morphology, chemical composition and growth mechanism on the photocatalytic activity and stability were methodically studied. The main contents are as follows:(1) ZnxCd1-xS alloyed films were prepared by simple chemical bath deposition. The morphologies, composition, structure, optical property and photocatalytic activity of the alloyed films can be easily controlled by adjusting the Zn/Cd molar ratios of the initial materials. The lattice structure ranges from primarily hexagonal Cd S to primarily cubic Zn S as x increases from 0 to 1, following with that the fluorescence intensity of the Znx Cd1-x S alloyed films increases gradually and the absorption edge exhibits a blue shift. The results show that reducing the zinc content can largely improve its absorption of visible light and enhance the photocatalytic activity for the degradation of organic pollutants.The degradation efficiency of Znx Cd1-x S is 21.2-80.2% under 4h visible light irradiation and the highest photocatalytic activity of Zn x Cd1-x S reaches when X=0.15 in the degradation of methyl orange(MO).(2) Zn0.2Cd0.8S alloyed films prepared by simple chemical bath deposition method. The effects of p H, annealing temperature and heating rate on the morphologies, composition, struction, optical property and photocatalytic activity of the Zn0.2Cd0.8S films are investigated. With the increase of p H, UV absorption band edge exhibits an obvious red shift and absorption peak strength increases.The grain size increases and crystallinity enhances for the Zn 0.2Cd0.8S alloyed films with increasing annealing temperature and heating rate. Moreover the absorption edge obviously shifts to longer wavelength withincreasing annealing temperature and the heating rate. Increasing annealing temperature and the heating rate can cement the photocatalytic activities of Zn0.2Cd0.8S alloyed films under visible light irradiation.(3) Novel Znx Cd1-x S/Ti O2 composite was fabricated through a facilechemical bath deposition method. Pure Ti O 2 is spherical nanoparticles with diameters of about 50-100 nm, whereas pure Zn x Cd1-x S is found to irregular particles with approximat ely 80 nm in dimensions. The Ti O 2 nanoparticles are distributed in the Zn x Cd1-x S crystallites and form a composite structure. The photocatalytic properties of Znx Cd1-x S/Ti O2 were evaluated by the photocatalytic degradation of MO under visible light and UV light irradiation. The results show that the formation of composite largely enhance the photocatalytic activity under visible light and UV light irradiation. Pure Znx Cd1-x S is unstable due to light corrosion, whereas the Zn x Cd1-x S/Ti O2 composite has almost no loss of photocatalytic activity after five recycles under the irradiation of visible light and UV light, indicating that composite has good photocatalytic stability. The remarkable photocatalytic activity of the Zn x Cd1-x S/Ti O2 composite may be derived from the effective separation of photogenerated electron-holes pairs owing to the formation of the interface between Zn x Cd1-x S and Ti O2 and their matching band positions. The photocatalytic activity reaches the highest when the amount of Ti O2 in the composite is 12%.(4) A novel ZnxCd1-xS/Ce O2 composite was fabricated through a facilechemical bath deposition method. The effects of process, composite ratio of Zn xCd1-xS/ Ce O2 composite on the morphology, composition,structure, optical properties and photocatalytic properties. The fluorescence spectrum peak of Znx Cd1-xS/Ce O2 composite lies at about 530 nm, and the emission peak intensity decreases with the increase of the molar ratio of Ce O 2. The results suggests that the electronic-hole recombination rate decreases, which improves the redox capacity of electron-hole pair and the photocatalytic activity of ZnxCd1-xS. The results show that ZnxCd1-xS /Ce O2 nanocomposite materials have potential application in photocatalytic degradation of organic pollutants.