Preparation And Gas Sensing Performance Of Carbon-based/?-Fe₂O₃ Nanocomposites

Metal oxide semiconductor?MOS?has a special response to most toxic and harmful gases due to unique chemical activity,electrochemical property,resistance taper.Because of this,MOS gas sensor has always been one of the most important research subjects of gas sensing research areas.Notably,Fe₂O₃,as gas sensing materials,has been applied to various gases qualitative identification and quantitative detection because of popular price,good stability,pretty high response and quick response speed.However,the high resistance of itself and poor selectivity limits the application in industrial inspection.For another,new carbon materials,such as graphene and carbon nanotubes with large specific surface area and high conductivity,have gradually emerged in the field of gas sensing in recent years.Nevertheless,the less detection species and long response/recovery time greatly limits the possibility of its further application.As thus,it is the key research direction of sensing materials that is prepared high response,quick response/recovery speed,wide detection range,specific selection,long service life sensing materials,which combined the advantages of carbon nanomaterials and Fe₂O₃.In this paper,polyhedral?-Fe₂O₃@RGO nanocomposites,sandwich-liked HP?-Fe₂O₃NRs/GOnanocompositesandflower-liked?-Fe₂O₃-MWCNTs nanocomposites were constructed respectively based on?-Fe₂O₃ and carbon materials.The composition,nanostructure and surface characteristic of these nanocomposites were characterized by SEM,TEM,XRD,FTIR,Raman,XPS and BET,and the gas sensing property was measured by the WS-30A gas sensing test system.Simultaneously,the relationship between structure and performance and the promoting mechanism of gas sensing were discussion.The main research as follows:?1?The polyhedral?-Fe₂O₃@RGO nanocomposites was prepared by mild hydrothermal method using the precursor??-FeOOH@RGO?,which was obtained by low temperature hydrolyzation.The polyhedral?-Fe₂O₃,with a size of 120-190 nm,was well dispersed on RGO surface.The sensor based on polyhedral?-Fe₂O₃@RGO nanocomposites has a high response towards acetone,which can touched 14.74towards 50 ppm acetone at 260°C.It was 1.6 times of pure?-Fe₂O₃.Meanwhile,the composites realized quick response/recovery and good selectivity towards acetone.The remarkable improvement of sensing performance profited from better conductivity,more active sites and stronger ability of gas adsorption.?2?Porous tripe-liked?-Fe₂O₃/GO/?-Fe₂O₃ nanocomposites with multistage structure were prepared by simple hydrolysis and annealing process.A mass of?-Fe₂O₃ nanorods with some 3-4 nm micropore arrayed on GO sheets uniformly.The morphology can regulate and control easily by the concentration of F^-,reacting temperature and reacting time.The gas sensing property of the composites has a higher response,faster response/recovery,better selectivity and good stability.Concretely,the response towards 50 ppm acetone touches 19.14 and the response and recovery time were 7 s and 8 s,respectively.It can hold on a stable value in 7 weeks.Big surface area and steady multistage structure,more active sites,synergistic effect between?-Fe₂O₃ and GO and heterojunction improved gas sensing performance overall.This provided a new thought that endow materials more physical and chemical properties by building unique nanostructure.?3?A flower-like?-Fe₂O₃-MWCNTs composite was prepared by green solvothermal method and annealing treatment.The diameter of the nanoscale?-Fe₂O₃flower is between 4⁸?m,and MWCNTs plays the role of bridging the nanoscale flower.The flake structure of the nanoscale is the result of the directional growth of?-FeOOH by selective adsorption towards SO₄^2-of?-FeOOH crystal faces.The response of the composites towards 50 ppm acetone touches 20.32 and the response/recovery time is 2.3/10.6 s under optimum operating temperature?220°C?.Obviously,the composites possess lower operating temperature,higher response,faster response/recovery speed and more excellent selectivity.The great promotion of gas sensing performance was due to the big surface providing more adsorbed sites active sites,the electrical bridge role of MWCNTs and the heterojunction between?-Fe₂O₃ and MWCNTs.