Fabrication Of Enhanced Adsorption Nano(Photo) Catalytic Materials For Air Purification

With the rapid growth of industrialization and the large-scale use of fossil fuels,the concentrations of volatile organic compounds?VOCs?and carbon dioxide?CO₂?in the atmosphere have increased significantly.Therefore,the air pollution has become more and more serious.No matter indoor or outdoor livings,human beings are breathing the air all the time.Therefore,the management of air pollution is closely related to the human health.Among the numerous air pollution sources,formaldehyde?HCHO?,a typical indoor VOCs contaminant,has received much attention due to its wide range of sources,high over standard rate and high risk.To remove the atmosphere HCHO,adsorption and thermal catalytic oxidation have been widely studied and made some progress so far.However,the exploration of new efficient adsorbents and catalysts is still the key problem.Note that,the control of indoor carbon dioxide?CO₂?concentration is usually been overlooked in the indoor air purification field.In fact,it causes chest tightness and headache when the concentration of CO₂ in the indoor air reached 3000-4000 ppm.Furthermore,CO₂ is one of the main greenhouse gases.In recent years,photocatalytic reduction of CO₂has attracted wide attention because it can reduce the concentration of carbon dioxide and convert the solar energy into high energy density of chemical energy.In order to further improve the formaldehyde or carbon dioxide removal efficiency,this work is based on summarizing the achievements of previous works,focused on the first key step of adsorption performance for formaldehyde or carbon dioxide and carried out researches on highly efficient adsorption enhanced catalytic system.The main experiment contents are as follows:Firstly,in order to improve the gaseous formaldehyde adsorption efficiency using titanate materials,hierarchical titanate nanospheres with in situ surface amine functionalization were prepared by the diethylenetriamine?DETA?mediated one-pot solvothermal process.The hierarchical assembled structure,specific surface area,pore volume and surface amine group of the as-prepared titanate samples can be well-tuned by varying the molar ratio of DETA and titanium butoxide?precursor?in the synthesis system.The excellent adsorption performance of titanate microspheres to remove formaldehyde is attributed to the synergistic effect of its hierarchical microstructure and surface amine functionalization.Secondly,porous TiO₂ is a typical indoor catalytic system support.Although we can obtain the porous TiO₂ simply through calcinations of titanate microspheres reported in previous section,this porous TiO₂ exhibited poor room-temperature formaldehyde oxidation performance even with the loading of Pt NPs.Therefore,in this chapter,hierarchical porous TiO₂ was prepared through a facile calcination approach,which used MIL-125?Ti?as precursor.The TiO₂ obtained by this strategy has large specific surface area and porous structure.Then,we deposited a certain amount of Pt NPs on the surface of the TiO₂.It was found that the obtained catalyses show good room-temperature formaldehyde oxidation performance.Thirdly,g-C₃N₄ is one of the most important visible-light-driven photocatalysts.However,its photocatalytic CO₂ reduction performance is not high.In this chapter,we report that the photocatalytic CO₂ reduction performance of g-C₃N₄ can be effectively improved by the combination of nanostructural design and surface structure modification.In detail,the protonated melamine was firstly prepared in glycol mediated with nitric acid aqueous solution.Subsequently,the protonated melamine was thermalyzed into the holey porous carbon nitride nanotubes.Afterward,the as-prepared tubular g-C₃N₄ was decorated with certain amount of transparent zeolitic imidazolate framework-8?ZIF-8?nanoclusters to further increase CO₂capture capacity without sacrificing of light absorption capacity.Because of the cooperative effects of nanostructural design and surface modification,photocatalytic performance of the optimized ZIF-8 modified tubular g-C₃N₄ photocatalysts was 3times higher than the bulk g-C₃N₄ photocatalyst for CH₃OH production.The result indicates the synergistic effect of nanostructural design and surface modification on the regulation of photocatalytic processes and properties.