Research On Photocatalytic Humidity-Controlling Materials

Indoor air environment includes thermal and humidity environment and air quality of indoor,which is essential for comfort and health of human.The use of air conditioning and fresh air system to adjust the indoor relative humidity for ensuring indoor air quality and high energy consumption will cause a huge environmental load.It is of great significance to combine photocatalysis and humidity control functions to prepare photocatalytic humidity-controlling materials for regulating indoor air environment of buildings.Based on the existing research,this study used sphagnum/diatomite and sphagnum/sepiolite humidity-controlling materials as nano-TiO2 carriers to prepare photocatalytic humidity-controlling materials.Through the glass chamber test,the humidity control and formaldehyde degradation properties,the main factors affecting the performance,and the optimal ratio of the two photocatalytic humidity-controlling materials were studied.Environmental scanning electron microscope(ESEM,energy spectrometer(EDS),Fourier transform infrared spectrometer(FTIR)and ultraviolet-visible spectrophotometer(UV-Vis)were used to analyze the humidity control and photocatalytic mechanism of optical materials.The research conclusion is as follows:(1)When using sphagnum/diatomite humidity-controlling material(GN-0)as nano-TiO2 carrier to prepare photocatalytic humidity-controlling material,TGN-1:6 photocatalytic adjustment prepared by TiO2:GN-0=1:6(mass ratio)have the best temperature and humidity adjustment and formaldehyde degradation;When using sphagnum/sepiolite humidity-controlling material(HN-0)as the carrier to prepare the photocatalytic humidity-controlling material,THN-1:4 photocatalytic humidity-controlling material was prepared by TiO2:HN-0=1:4(mass ratio),whose temperature and humidity adjustment and formaldehyde degradation are the best.Loading nano-TiO2 on the humidity-controlling material can improve the photocatalytic reaction activity.Both composite materials have a certain formaldehyde degradation ability under natural light.Ultraviolet light can improve the formaldehyde degradation ability of the material.(2)UV-Vis analysis showed that the forbidden band widths of sphagnum/diatomite-based and sphagnum/sepiolite-based photocatalytic humidity-controlling materials were 3.08 eV and 3.28 eV,respectively,which were narrower than the nano-TiO2 band gap(3.35 eV).The diatomite and sepiolite materials contain silicon hydroxyl groups and hydroxyl groups,which generate electronic interaction energy with nano-TiO2,generate more Bronsted acid sites,and promote photocatalytic reactions.(3)Because the specific surface area of sphagnum/diatomite-based humidity-controlling materials and the ratio of mesopores?10 nm are larger than those of sphagnum/sepiolite-based humidity-controlling materials,and the nano-TiO2 is more evenly distributed on the surface of the sphagnum/diatomite-based humidity-controlling material,the capillary channel effect of the sphagnum/diatomite-based photocatalytic humidity-controlling material is better,and the width of the forbidden band is narrower.Therefore,the performance of humidity control and formaldehyde degradation is better.(4)The combination of the photocatalysis and humidity-controlling functions of the material enables the photocatalysis to degrade formaldehyde adsorbed in indoor air and humidity-controlling materials when there is daylight;even if there is no photocatalysis at night.Because the low formaldehyde concentration material can absorb a certain amount of formaldehyde,it can still reduce the formaldehyde concentration in the indoor air.That is,the material can produce a photocatalytic-adsorption synergistic effect to achieve the purpose of regulating the indoor air environment.