Study On Preparation Of TiO₂/CdS Composites And Their Visible-light Photocatalytic Properties

Since the 21st century,with the improvement of people’s living standards,the consumption of energy is increasing day by day.At the same time,the environmental pollution is becoming more and more serious.Energy and environmental problems have become increasingly prominent key issues and the biggest challenge in the world.If solar energy can be exploited to solve these problems of environmental pollution and energy shortage,the crisis will be effectively alleviated.Therefore,photocatalytic technology is a very popular research direction in recent years,attracting wide attention.Photocatalytic technology can not only decompose water to produce hydrogen,but also degrade pollutants.It has the advantages of low cost,low secondary pollution and mild reaction conditions.It provides us with an effective way to harness the environment and utilize solar energy.TiO2 is a cheap,non-toxic,environmentally friendly,stable chemical property and strong absorptive photocatalyst.It has been deeply studied in the degradation of pollutants and the decomposition of water to produce hydrogen.However,because of its wide band gap,it can only absorb about 5%of the ultraviolet light,resulting in about 50%of the visible light can not be used.At the same time,some electron hole pairs excited by ultraviolet light are easy to recombine,which greatly limits the photocatalytic performance.In this experiment,CdS with narrow band gap was modified with TiO2 to increase its visible light activity and reduce the electron-hole coincidence rate,so as to improve the photocatalytic efficiency.In this paper,using cadmium chloride,sodium sulfide and tetrabutyl titanate as raw materials,TiO2/CdS composites with different titanium-cadmium ratio and hydrothermal reaction time were prepared by one-step hydrothermal and two-step hydrothermal/solvothermal synthesis methods respectively.The purpose of compounding TiO2 with CdS was achieved.The composition and structure of the composites were tested and characterized by Scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),UV-vis spectroscopy.The photocatalytic properties of the composites with different Ti/Cd ratios,different hydrothermal reaction time and different catalyst content were tested under the light of 395,425 and 465nm wavelengths,respectively.The results show that TiO2/CdS composite prepared by hydrothermal synthesis has excellent photocatalytic properties and visible light activity.By one-step hydrothermal synthesis,20 mg/L methylene blue solution could be completely degraded at room temperature for 140 min under the conditions of Ti/Cd ratio of 2:1,hydrothermal reaction of 18h and photocatalytic wavelength of 465 nm.The results show that the nanocomposites of TiO2/CdS have good visible light activity and broad application prospects in the field of photocatalysis.