Study On Preparation And Properties Of Cobalt Titanate Materials With Multi-scale Pore Structure

The main problems in the application of cobalt titanate materials in gas sensitivity are poor detection sensitivity to low concentration gases,slow response speed and high operating temperature.It is an important research direction to improve the sensitivity of gas sensing materials by regulating the surface morphology and internal pore structure characteristics.Multi-scale structure can provide more gas diffusion channels and more effective active sites,which plays an important role in improving the gas sensing properties of materials.Therefore,it is of great theoretical significance and practical application value to explore the preparation process and regulation methods of CoTiO₃ materials with multi-scale pore structure.In this dissertation,multi-scale structured CoTiO₃ materials with different morphologies were prepared by solvothermal method.The samples were characterized by XRD,SEM,TEM,BET,UV-Vis,FTIR,Raman and PL.The effects of volume ratio of mixed solvent and various surfactants on structural evolution of porous CoTiO₃ materials were discussed and the corresponding influence mechanisms were analyzed.The gas sensing properties of different structural samples were analyzed by comparing the detection of ethanol gas.（1）Porous CoTiO₃ aggregates with different morphologies were prepared using titanium salt and cobalt nitrate as raw materials,by regulating the volume ratio of ethylene glycol（EG）to anhydrous ethanol in the mixed solvent without template agent participation.As the volume ratio of ethylene glycol to anhydrous ethanol reached 1:2,the prepared CoTiO₃powders with multi-scale pore structure were aggregated by uniformly dispersed spherical-like particles with interconnected pore channels between the particles,and the pore sizes were distributed in the ranges of 2-10 nm and 40-200 nm.The as-prepared porous CoTiO₃ exhibited high sensitivity（20.3）,rapid response time（7 s）and good long-term stability to 20 ppm ethanol at working temperature 300℃.（2）In the solvothermal preparation process assisted by cetyltrimethylammonium bromide（CTAB）,the porous CoTiO₃ materials with multi-scale pore structure were prepared under ethanol solvothermal treatment at 200℃for 18 h when the molar ratios of CTAB/Ti/Co and H₂O/Ti/Co were 1/3/3 and 12/1/1,respectively.The specific surface area of prepared porous CoTiO₃ was 11.305 m²/g and the pore sizes were distributed in the ranges of2-5 nm and 20-100 nm.The sensitivities of porous CoTiO₃ materials to 20,50 and 100 ppm ethanol gases at working temperature 300℃were 37.3,69 and 93,respectively.（3）CoTiO₃ microspheres with core-shell structure were prepared by the synergistic action of polyethylene glycol-2000（PEG-2000）and diethanolamine（DEA）under ethanol solvothermal treatment at 200℃for 18 h,when the molar ratios of DEA/Ti/Co,PEG-2000/Ti/Co and H₂O/Ti/Co were 3.2/1/1,0.04/1/1 and 12/1/1,respectively.The thickness of the shell was about 170 nm and the pore sizes were mainly distributed in the ranges of 2-5 nm and 10-70 nm.The sensitivities of core-shell CoTiO₃ microspheres to 20,50and 100 ppm ethanol gases at working temperature 300℃were 22,66.7 and 108,respectively,and the response and recovery time were about 8 s and 29 s to 50 ppm ethanol.