Fabrication Of SnO₂/g-C₃N₄ Composite For Better Photocatalytic And Gas-sensitive Properties

With the development of science and technology,the technology of sensors is gradually integrated into all walks of life.As an important branch of the technology of sensors,gas sensor are more and more closely connected with people's work and life.From food production and gas leakage to aerospace and defense military,gas sensors are indispensable.Gas sensor is a detection device which can transform the information of gas concentration into electrical signal.Its core is gas sensitive material.Among the gas sensitive materials,semiconductor materials have been paid more attention.In this paper,starting from the metal oxide semiconductor material Sn O₂,in order to further improve its performance,Sn O₂ and g-C₃N₄ materials were compounded,and the properties and performance of the materials were analyzed by the techniques of SEM,XRD,UV-Vis,BET,TEM,XPS etc.The photocatalytic and gas-sensitive properties of the materials were also studied.By the techniques of SEM and TEM,it can be observed that g-C₃N₄ is a layered nanosheet,and Sn O₂ is randomly distributed on the surface of g-C₃N₄.By the technique of XRD,it can be found that the XRD curve has five distinct diffraction peaks corresponding to the five crystal planes of the tetragonal rutile structure Sn O₂(JCPDS Card No.41-1445),and the diffraction peaks of g-C₃N₄ are observed.The band gap values of Sn O₂ and g-C₃N₄ are estimated to be 3.04e V and 2.06e V respectively according to the equation(Ah?=k(h?-E_g)ⁿ),and the band gap value of Sn O₂/g-C₃N₄ composite is estimated to be about 2.67e V according to the equation(E_g=1240/?).The surface valence states of the composites were analyzed according to XPS spectra,and electron transfer between Sn O₂ and g-C₃N₄ was deduced.In addition,the photocatalytic degradation of Rh B was carried out by a self-made degradation device,and the degradation rate constants of different materials were analyzed and compared by kinetic equation.The results show that Sn O₂/g-C₃N₄ composites have better photocatalytic performance than pure Sn O₂ and g-C₃N₄.The photocatalytic mechanism is explored as follows:The surface redox potential of Sn O₂/g-C₃N₄composite is further improved than the pure Sn O₂ and g-C₃N₄,so the photocatalytic performance of the materials is further improved.The gas-sensitive properties of the materials were tested by the gas-sensitive element tester,and the results show that Sn O₂/g-C₃N₄ composites have better gas-sensitive properties than the pure Sn O₂ and g-C₃N₄.Among them,the third sample(g-C₃N₄:Sn O₂=0.5:0.45)has the best gas sensitivity.Methanol,ethanol and isopropanol are the target gases with the best gas sensitivity,but the active stability of the materials is insufficient,and the long-term stability is satisfactory.Finally,the gas-sensitive mechanism is explored as follows:the heterogeneous structure of Sn O₂/g-C₃N₄composite inhibits the recombination of electrons and holes,and electrons are faster transfered to the surface of the material,resulting in improved gas sensitivity.