Gas Sensing Properties Of Titanium Dioxide And Titanate Nanomaterials

Gas sensors have been widely used in many fields such as air purification,medical treatment,etc.However,most gas-sensitive materials are difficult to balance various gas-sensitive properties.For example,metal oxide semiconductor materials have the advantages of low cost,simple manufacturing,high sensitivity,fast response,long service life,etc,but also have disadvantages such as high operating temperature,poor selectivity and stability.Therefore,it is very important to improve the performance of gas sensing materials and develop novel gas-sensitive materials.In this paper,we successfully prepared three kinds of gas-sensitive materials including amorphous titanium dioxide(A-TiO₂),iron titanate and copper titanate nanomaterials.The gas-sensitive response and response mechanism of these nanomaterials toward ethanol(C₂H₅OH)and ammonia(NH₃)were studied systematically,and the impact of humidity on the gas sensitivity of the sensors was investigated further.The specific research content is as follows:1.The A-TiO₂ porous nanospheres with a specific surface area of 509.8 m²g^-1 were successfully prepared by a simple sol-gel method,which exhibited a p-type response to100 ppm C₂H₅OH at room temperature with a sensitivity of 2.361.At 277.1°C,the response type of A-TiO₂ converted to n-type with a sensitivity of 2.046,which is related to the different ways in which O^-_adsadsorbed on the surface of A-TiO₂ at different temperatures.After three months of repeated experiments,the response of the gas sensor has no obvious change,which demonstrates its application prospects in the field of C₂H₅OH detection.2.The iron titanate and copper titanate nanomaterials were successfully synthesized via a simple hydrothermal method and a cation substitution process by using the prepared A-TiO₂ porous nanospheres as precursors.The specific surface areas of these two nanomaterials are as high as 172.8 m²g^-1 and 189.7 m²g^-1,respectively.Gas sensing experiments showed that these two nanomaterials have obvious response toward C₂H₅OH and NH₃ at room temperature.After exploring the optimal working temperature,it was found that the iron titanate nanostructure had a sensitivity of 10.625to 100 ppm C₂H₅OH at 150.4°C,and the sensitivity of copper titanate nanomaterials toward 100 ppm C₂H₅OH and 100 ppm NH₃ at 131.4°C was 3.622 and 3.125respectively,which is attributed to the fact that Fe³⁺and Cu²⁺can be oxidized at high temperatures,and a large surface area p-n heterojunction with titanate can be formed.In addition,both Fe₂O₃ and Cu O have the ability to rapidly transport electrons and efficiently catalyze oxidation.The sensors all have good C₂H₅OH selectivity and good detection stability(over 210 days).3.The effects of environmental humidity on the properties of amorphous titanium dioxide,iron titanate and copper titanate gas-sensitive nanomaterials were studied.The difference in ambient humidity often causes changes and drifts in the baseline resistance and sensitivity of the gas sensitive materials,which affects the practical application of gas sensors.In this work,it is found that the resistance value and sensitivity of the gas sensitive materials decrease with the increase of the ambient humidity and the degree of change gradually decreases.It is considered that this is related to the water molecule occupying the surface active site of the gas sensitive materials.