The Hydrothermal Systhesis,Gas Sensing Properties And Electroc Hemical Properties Of Zn²⁺ Induced Spherical Urchin Like SnO₂ Nanomaterials

In this thesis,Zn²⁺doped spherical urchin like SnO₂ nanomaterials had been synthesized via a simple and convenient hydrothermal method,which used Zn²⁺as dopant.The influence of synthesis parameters and doping amount had been discussed and the influence rule had been found via a detail analysis.Subsequently,the controllable synthesis of Zn²⁺doped spherical urchin like SnO₂ nanomaterials had been realized.The morphology,phase,composition and photoelectric property of Zn²⁺doped spherical urchin like SnO₂ nanomaterials was characterized by SEM,TEM,XRD,XPS and so on.And the formation mechanism had been discussed meticulously.On the basis of above,the gas sensing performance of Zn²⁺doped spherical urchin like SnO₂ nanomaterials had been explored.The influence of hydrothermal time,hydrothermal temperature and Zn²⁺doping amount been studied systematically.The gas sensing mechanism had been discussed meticulously.Not only that,the electrochemical performance as negative electrode materials of supercapacitor had been studied initially.The results showed that the optimum synthesis parameters of Zn²⁺doped spherical urchin like SnO₂ nanomaterials were as follows:the hydrothermal temperature was 190 ℃,the hydrothermal time was 24 hours,the ratio of Zn²⁺doping amount and Sn⁴⁺was 1 to 1,the volume ratio of deionized water and ethanol absolute was 2 to 1,the urea amount was 18 mmol and the sodium dodecyl sulfate（SDS）amount was 4 mmol.The characterization results showed that the Zn²⁺doped spherical urchin like SnO₂ nanomaterials was indexed to the phase of rutile type SnO₂with the tetragonal crystal system.Its main exposed crystal plane was（101）,which is a high energy plane.The chemical valence of Sn and O atom in the SnO₂ was+4 and+2,respectively.The states of the O on the surface of SnO₂ were O_lattice,O_x^n-and O_OH.According to the influence of all the synthesis parameters,this thesis put up the the formation mechanism of Zn²⁺doped spherical urchin like SnO₂ nanomaterials,which could be divided into six stages included hydrolyzation,dehydration,nucleation-growth,ripening,self-assembled and orientated growth.At the beginning,the ZnSn（OH）₆ crystal nucleus was formed via the reaction of Na₂SnO₃ between Zn（CH₃COO）₂,which was with the hydrolyzation of them.And then,the growth of ZnSn（OH）₆ crystal nucleus taken place and the crystal grain was formed.Subsequently,according to the mechanism of Ostwald ripening mechnism,the crystal grain grown into cube-like ZnSn（OH）₆.Then,the clusters of cube-like ZnSn（OH）₆was formed via self-assembled process.At last,Zn²⁺doped spherical urchin like SnO₂nanomaterials would formed via the orientated growth process under the induction of Zn²⁺and hydrothermal condition.In this thesis,the Zn²⁺doped spherical urchin like SnO₂ nanomaterials had employed as gas sensing materials to explore the gas sensing performance.The results showed that the sensitivity to 200 ppm ethylene glycol had reached to 61 at the optimum voltage of 3.5 V.The response time and recovery time was 90 s and 32 s,respectively.All of those demonstrated that the Zn²⁺doped spherical urchin like SnO₂nanomaterials exhibited a good gas sensing performance to ethylene glycol.In the meantime,the influence of hydrothermal time,hydrothermal temperature and Zn²⁺doping amount to the gas sensing performance of Zn²⁺doped spherical urchin like SnO₂ nanomaterials had been explored.The test results showed that:（1）A relative low doping amount of Zn²⁺didn’t good in regard to the gas sensing performance to ethylene glycol.Only when the ratio of Zn²⁺doping amount and Sn⁴⁺was 1 to 1 could the gas sensor exhibit a good gas sensing performance to ethylene glycol.（2）Both a long or a short holding time were not good to the gas sensing performance to ethylene glycol and the optimum holding time was 24 h.（3）At a relative low hydrothermal temperature,the optimum operation voltage was relative high.When the hydrothermal temperature was up to 190 ℃,the optimum voltage was low and the sensitivity was high.Finally,the electrochemical performance of Zn²⁺doped spherical urchin like SnO₂ nanomaterials as the electrode of supercapacitor had been explored.The test results showed that the electrochemical performance of Zn²⁺doped spherical urchin like SnO₂ nanomaterials as negative electrode meterials of supercapacitor was not as good as expected.