Preparation And Photoelectrochemical Properties Of SnO₂-based Composite Nanomaterials

Tin dioxide?SnO₂?is a traditional environmentally-friendly semiconductor,and has been widely used in photocatalysis,gas sensing,and many other areas because of its excellent photoelectrochemical properties and low price.However,as the semiconductor with a wide bandgap,SnO₂ could only absorb the ultraviolet light,resulting in the low utilization of solar energy.Besides the high recombination rate and short lifetime of photogenerated carriers,low quantum efficiency,and easy agglomeration of powder nanomaterials which are difficult to be separated from the liquid,all of these problems limit the commercial application and development of SnO₂.Based on the above problems and challenges,we used the electrospinning technology combining with the hydrothermal method to prepare SnO₂-based composite nanomaterials with different structures.The effects of the morphology and microstructure on the photoelectrochemical properties of SnO₂-based composite nanomaterials were studied.The major content of the researches is summarized as follow:?1?SnO₂-core carbon-shell composite nanotubes were synthesized by electrospinning technology combining with hydrothermal method for the first time.The high adsorption ability of carbon layer is beneficial to the interface reaction,and the visible light absorption ability of carbon layer is expected to sensitize SnO₂,thus realizing a visible light-responsive photocatalyst with high photocatalytic efficiency.The microstructure and morphology showed that the graphitized carbon layer grew uniformly on the inner and outer walls of SnO₂ nanotubes through the C-O-Sn bond.The thickness of the carbon layer could be controlled from 2 nm to 8 nm by changing the concentration of the precursor.The photoelectrochemical performance showed that SnO₂-core carbon-shell composite nanotubes had the visible light absorption capacity.The photocurrent of SnO₂-core carbon-shell composite nanotubes with 5wt% carbon was four times higher than that of SnO₂ nanotubes under the ultraviolet light irradiation,and showed obvious photocurent and best photocatalytic activity toward 4-nitrophenol under the visible light irradiation.In addition,SnO₂-core carbon-shell composite nanotubes maintained the nano-mesh structure of SnO₂ nanotubes,which could be separated from the liquid by simple filtration to avoid secondary pollution and to be reused.?2?Monodispersed SnO₂@SnS2 flower-like composites were prepared through ion-exchange method using the electrospun SnO₂ nanotubes as substrate for the first time,and applied on the photocatalytic reduction of Cr6+-containing toxic solution.The morphology study showed that there was no reunion phenomenon among SnO₂@SnS2 composites and they were uniformly dispersed.Photoelectrochemical performance revealed that,compared with SnO₂ nanotubes,SnO₂@SnS2 composites with different components showed enhanced absorption to visible light to different degrees,the photoluminescence intensity?PL?of which decreased significantly,and showed excellent photocatalytic reduction activity toward Cr6+-containing toxic solution under visible light irradiation.The enhanced photoelectrocatalytic properties may be attributed to the addition of SnS2 with the narrow bandgap and the construction of heterostructure.?3?SnO₂ nanotubes@TiO2 nanorods heterostructure composites were prepared through one-step hydrothermal method using the electrospun SnO₂ nanotubes as templates for the first time.The space lattice simulation revealed that the lattice mismatch of TiO2?110?plane and SnO₂?110?plane is only 2.98%.Therefore,the TiO2 nanorods could grow in the [001] direction perpendicular to the surface of SnO₂ nanotubes to form the SnO₂ nanotubes@TiO2 nanorods heterostructure composites.SnO₂ nanotubes@TiO2 nanorods heterostructure composites kept the structure of SnO₂ nanotubes and owed high length-to-diameter ratio and specific surface area,which were helpful for contacting fully with the chemicals and promoting the transportation of chemicals and charges.Thus,compared with SnO₂ nanotubes,SnO₂ nanotubes@TiO2 nanorods heterostructure composites showed better gas sensitivity and gas selectivity in the gas-sensing test.The response time and recovery time of the best sample toward acetone gas at 5 ppm is 5.4 s and 6.2 s,respectively.