Synthesis of functional group modified defective titania hydrogel at low temperature and normal pressure and its application in degradation of formaldehyde released from coatings
[Introduction]Formaldehyde released from coatings is a common air pollutant,known for its pungent odor and potential health hazards.TiO2 photocatalytic degradation technology is widely adopted as an environmentally friendly method for formaldehyde removal.[Method]Functional group-modified TiO2 photocatalysts were prepared based on defective TiO2 hydrosol(PTC)with hydroxylamine solution,methylamine solution,hydrazine hydrate,methanol,or hydrogen peroxide solution as modifier.Their photocatalytic performance for formaldehyde degradation was then studied.The composition,structure,and photoelectrochemical properties of the photocatalysts were characterized by using X-ray diffraction(XRD),nitrogen adsorption/desorption,transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis),fluorescence spectroscopy,and electrochemical measurements.[Result]The TiO2 photocatalyst modified with hydroxylamine exhibited the best performance.Under ultraviolet irradiation,it achieved a formaldehyde degradation efficiency of 73.3%within 2 hours,which was 36 times higher than that without any catalyst and 3.6 times higher than that of unmodified PTC.[Conclusion]Due to the modification of functional groups,defect energy levels are formed between the low-energy valence band(VB)and the high-energy conduction band(CB)of TiO2.When TiO2 is irradiated by light,these defects can act as traps to capture photogenerated carriers,enhancing the light absorption capacity and the separation efficiency of photogenerated carriers.This rapidly generates highly oxidative reactive oxygen species,thereby facilitating the photocatalytic degradation reaction.
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