Preparation And Catalysis Of SiO₂ Aerogel Doped With Metal Ions

Aerogels,as a new porous material with strong functionality,large specific surface area,high porosity and good chemical stability,have attracted much attention and have been widely applied in many fields such as medicine,insulation and catalysis.The supercritical drying method is usually used to prepare block aerogels with good performance,but this method also has risks:high temperature and high pressure,and the flammability and time consuming of the solvents can not achieve large-scale industrialization.In this paper,subcritical drying method is adopted to reduce the equipment cost,reliable and repeatable,and make the production process more economically feasible and expand the application scope of atmospheric gel.In this paper,Fe³⁺doped TiO₂aerogels were prepared by sol gel method under the condition of sub critical drying using TBOT as precursor.The results showed that the prepared Ti O₂aerogels had large specific surface area,the specific surface area of the iron doped aerogels was 497.20-503.15 m²/g,and the volume and average pore size increased.After Fe³⁺doped,the light response of Ti O₂can be changed from ultraviolet light to visible light,which expands the light response range of Ti O₂.The fluorescence intensity decreased,indicating that the recombination rate of excited electron hole decreased.In the experiment of photocatalytic CO₂methanol synthesis,Ti O₂aerogels showed better photocatalytic performance than P25.When the reaction time was 4 h,the yield of methanol was 370.16?mol?g^-1over P25.The yield of methanol was 711.80?mol?g^-1over TiO₂aerogel,which was 92.30%higher than over P25.The iron doped aerogels show better catalytic performance.When the Fe³⁺content was 3%,the yield of methanol was2198.43?mol?g^-1,which was 493.91%higher than over P25.When the doping amount is5%,the methanol yield decreases slightly and the catalytic performance decreases.In this paper,Ti⁴⁺doped SiO₂aerogels were prepared by using sol-gel method and subcritical drying conditions with TBOT and TEOS as precursors.The results showed that the aerogels prepared were highly amorphous and had a large specific surface area of817.83 to 854.91 m2/g,and Ti⁴⁺was evenly distributed in the Si O₂aerogel framework.In the epoxidation reaction of cyclooctene with hydrogen peroxide,amorphous titanium silicon aerogel has better catalytic effect.Characterization methods like BET,TEM,SEM,FTIR,XRD,UV-Vis,PL,XPS,UPS were used to test the specific surface area,morphology,molecular structure,the crystal structure,visible absorption intensity,electron-hole recombination rate,element valence state and energy band structure performance.