Preparation Of Bi-based Multi-element Metal Oxides And Research On Its Gas-sensing Properties

In recent years,with the development of global industry,kinds of poisonous and harmful gases produced in industrial production,which are seriously harmful to human beings.Therefore,it is crucial to develop the high-performance gas sensor for real-time environmentalmonitoring.Metal oxide semiconductor(MOS)gas sensors have attracted widely attenting owing to its irreplaceableadvantages.A lot of works have been carried out to enhance the gas-sensing properties of single oxides,but the unsatisfactory selectivity always restricts its practical application seriously.As we know,binary oxide semiconductors possess more abundant structure types and corresponding outstanding physical and chemical properties comparing single oxides.Recently,binary oxide semiconductors have attracted extensive interest in the field of gas sensing.As the typical representatives of binary metal oxide semiconductor,BiVO4 and CuBi2O4 have been successfully applied for photocatalyst and degradation of organic pollutants owing to their specific structures.Usually,the performance of metal oxide semiconductor-based gas sensorsare closely related with the carrier transport properties as well.Thus,BiVO4 and CuBi2O4 could be potential candidatesas gas sensing materials.Till now,the research about gas sensing properties of BiVO4 and CuBi2O4 is very rarely reported,so there are many problems need to be solved.Therefore,the following studies focusing on these two materials were carried out:(1)The pure BiVO4 was successfully synthesized by the coprecipitation method firstly.Which manifest outstanding selectivity toH2S gas.Further,Mo6+ was taken as the dopant to enhance the gas sensing properties,XRD and XPS results indicated that,Mo6+doping could induce great phase transition,affecting the crystallography of BiVO4 and promoting oxygen vacancy formation.The further sensing detection displayed that oxygen vacancy could provide more active sites during the sensing reaction and increase the gas adsorption on the surface of the sensing materials.Thus,we can confirm that dopant Mo6+ in BiVO4 is a promising strategy to improve the gas sensing performance.(2)Based on a facile approach of laser irradiate in acetone medium,the crystallinity and the concentration fo oxygen vacancy of BiVO4 were enhanced,resulting in highly improved sensing response to H2S.The SEM and TEM results indicate that the morphology of BiVO4transform from polyhedron to spherical-like structure and the diameters of the sphere changed with the irradiation energy.Further,XPS analysis manifest that the sample under irradiation with 100 mJ can produce more oxygen vacancy concentration than others and with most oxygen vacancy concentration compared with other samples and exhibits a best performance and excellent selectivity to H2S.(3)A series of CuBi2O4 microspheresare with tuning morphology and the concentration of oxygen vacancy were synthesized via a coprecipitation route through controlling the proportion of solvents,or the concentration of NaOH.The concentration of oxygen vacancy in CuBi2O4 is closely realted with the gas sensor response.In order to further improve the crystallinity and concentration ofoxygen vacancy,the irradiation with 532 nm laser was also carried on for the CuBi2O4.XPS analysis indicates that,CuBi2O4-sample under irradiation of 100 mJ contains most oxygen vacncy compared with other samples,which results in best sensing response to ethanol gas.