Synthesis Of Metal Oxide/Graphene Composite And Investigation Of Its Gas Sensing

With the development of chemical industry,the demand of ammonia and xylene gas sensors have been improved,for both the environment pollution and human's security awareness have been gradually increased in recent years.To the best of our knowledge,ammonia and xylene gas sensors based on metal oxide nanomaterials have attracted great attention due to their low cost,high response and facile synthesis.However,several key shortcomings,such as high operating temperature,more power consumption and poor selectivity,which restricted their applications.Therefore,developing a new gas sensor material which showed enhanced sensitivity and excellent selectivity at room temperature is desirable.Among different kinds of metal oxides,Co3O4 attracted great interest because of its wide applications in various fields,such as electrochemical sensors,eletrocatalysts,supercapacitors,gas sensors and lithium ions batteries.Besides,Co3O4 was obtained by the calcination of Co(OH)2,which was the precursor of Co3O4.Co(OH)2 was fabricated by fast etching of cuprous oxide,showing high specific surface area and hierarchical structure,which is beneficial to the diffusion of the gas and ions.Therefore,in the Chapter 2,the Co(OH)2 hollow spheres were synthesized based on fast etching of polycrystalline Cu2O,which was applied for non-enzymatic electrochemical detection of glucose simultaneously for the first time,for it owns great specific surface area,which is favorable to the diffusion of ions.Nanocomposites gradually came into our field,for so many researches have been studied on the detection of gas sensors based on pure Co3O4.Herein,in the Chapter 3,the hierarchical Co(OH)2 hollow spheres were fabricated based on the fast etching of cuprous oxide,and then the Cr was introduced into the solution of Co(OH)2.After calcination,the Cr/Co3O4 composite was obtained,and it was applied to the detection of xylene.Compared with the pure Co3O4,the results of the Cr/Co3O4 composite showed better response,enhanced sensitivity and excellent selectivity.In order to further solve the high operating temperature of both the pure Co3O4 and Cr/Co3O4 composite,the graphene was introduced into the pure Co3O4,and the results revealed that the gas sensor could be detected at room temperature.Nevertheless,in Chapter 4,the Co3O4/rGO was synthesized on the fast etching of cuprous oxide/graphene oxide nanocomposites and then with a heating process,and it was applied to the detection of ammonia.The results revealed that the obtained nanocomposites showed good response and excellent selectivity at room temperature.