Structural Design,Preparation And Photoelectrochemical Properties Of Tin Oxide Nanocomposites

Tin oxide?SnO₂?,as a typical n-type semiconductor material with a wide band gap,has been widely used in various fields because of its excellent stability,optical performance,catalytic performance and high lithium storage capacity.For practical applications,however,SnO₂ materials still encounter some serious problems to be resolved.For example,the poor response to visible light limits the effective utilization of solar spectrum for photocatalytic applications,and the material structure is prone to collapse during the process of charging and discharging for lithium-ion battery applications.These drawbacks would hamper the photoelectrochemical applications of SnO₂ materials.In this work,a series of SnO₂-based structures were designed and synthesized,and their photoelectrochemical performances?such as: photocatalysis and electrochemical lithium storage?were improved by means of modification methods including coating,semiconductor coupling,and metal doping.The main contents in this work are given as follows:1.Preparation and photoelectrochemical performances of CuO@SnO₂ hollow microspheresUsing SiO₂ microspheres as template,SnO₂@SiO₂ microspheres were firstly prepared by a hydrothermal method.Hollow CuO@SnO₂ microspheres were then obtained throughthe coupling of solution impregnation,aging,calcination and etching process.The photoelectrochemical performances of the as-prepared products were also evaluated.The experimental results demonstrate that compared with SnO₂ microspheres,hollow CuO@SnO₂ microspheres possessed much better photocatalytic activity and electrochemical lithium storage performance,which could be attributed to the surface-wrapped CuO.In terms of photocatalysis,the enwrapped CuO could not only broaden the light spectral absorption scope,but also facilitate the separation of photo-generated carriers,thus improving the photocatalytic degradation efficiency.With respect to the electrochemical lithium storage,the enwrapped CuO could enhance the charge transfer rate and provide the electrode support materials to relieve the structural collapse of SnO₂,thus improving the electrochemical lithium storage performances of SnO₂ anode materials.2.Preparation and electrochemical lithium storage performance of SnO₂/C composite microspheresThe carbon microspheres were firstly prepared by a hydrothermal method,and SnO₂/C composite microspheres were then obtained by impregnating carbon microspheres in the aqueous solution of Sn Cl2 followed by a calcination process in inert atmosphere.The electrochemical experiments indicate that the SnO₂/C composite microspheres possessed a higher reversible capacity than C microspheres and also exhibited better cycle performance than SnO₂ nanocrystals.The enhanced electrochemical performances could be ascribed to the enhanced conductivity of SnO₂/C composite microspheres as well as the improved structural stability arising from the restrained structural collapse induced by the coupling of carbon microspheres on the premise of sacrificing some capacity.3.Preparation and photocatalytic performances of Zn-doped SnO₂ nanostructuresZn-doped SnO₂ nanostructures were prepared by using a one-pot hydrothermal process,and their photocatalytic performances were then examined.Experimental results indicate that cystal lattices in Zn-doped SnO₂ nanostructures would directionally grow up without changing the original SnO₂ crystal lattice under the hydrothermal conditions of high temperature and high pressure.Compared with the pure SnO₂ sample,Zn doped SnO₂ sample possessed improved photocatalytic activities.The enhanced photocatalytic performances could be attributed to the improved carrier mobility of photogenerated carriers arising from the increased lattice order degree in Zn-doped SnO₂,the increased reactive sites on the surface of Zn-doped SnO₂ induced by the doping defects,as well as the self-trapped capture of phtogenerated electrons induced by the surface oxygen vacancies in Zn-doped SnO₂,thus facilitating the separation of photo-generated carriers.