CeO 2 Doped Oxidized Graphite Composites And NO X Gas Sensing Properties

In this thesis, two kinds of metal oxide/graphite oxide-doped CeO2 composites which had excellent gas sensing performance were designed and already prepared by reflux method. The structure and morphology of the as-obtained product were characterized by using X-ray diffraction, Fourier transform infrared spectroscopy and Scanning electron microscopies. The results indicated that the synthesized gas sensing materials poss unique structure with high performance. The main research contents are as following.(1) CeO2/NiO/GO composite(CNG) has been synthesized with a two-step synthetic method. Firstly, the composite precursors have been prepared by reflux method, after calcinated under N2 atmosphere the CNG were synthesised. The gas-performance of the composites for NOx at room temperature has been tested. Studies have shown that the 3D flower-like structure assembled by numerous thin nanosheets. The synthesis of CNG-5 sensor exhibits excellent gas-sensing properties to NOx at room temperature, the sensitivity could reach 75.32% under 97 ppm NOx, the response time was 10.67 s and the low detection limit was 0.97 ppm. The gas sensor also showed excellent selectivity and stability to NOx. The enhancement in gas sensing performance was attributed to the modification of CeO2, which can increase the surface area of materials and benefit for the diffusion of the target gas. Meanwhile the adding of GO as carbon substrate could also increase the conductivity of composite and well improve the gas sensing performance of NOx.(2) CeO2/In2O3/GO composite(CIG) has been synthesized via reflux method by using graphite oxide as carbon source, indium nitrate and cerium nitrate as metal salts, urea as precipitant. We investigated the sensing performance of the fabricated CIG nanohybrids towards NOx in air at room temperature. The results indicated that the synthesized CeO2/In2O3/GO nanostructures were composed of irregular nanosheets with numerous pores. Futhermore, the CIG-5 sensor has ultra-high sensitivity and much faster response than other gas sensor materials. It exhibited excellent gas-sensing properties with gas response of 125.89 and the response time of 44.67 s to 97 ppm NOx at room temperature.