VUV/β-Ga₂O₃ Photocatalytic Degradation Of VOCs In Indoor Air

As increasing of dependence on indoor environment, people has paid more andmore attention to the indoor air quality (IAQ). Photocatalytic oxidation (PCO), as anadvanced oxidation technology, has potential values for application in indoorpollutants treatment. In this dissertation, a simple, mild and low-cost hydrothermalmethod was used to prepared high efficientβ-Ga₂O₃ with special microstructure byoptimizing the material growth conditions, to solve main photocatalytic bottlenecks,including high photoinduced hole-eletron recombination rate and low photocatalyticefficiency. Also, the relationships between morphology, crystallization, opticalproperties with photocatalytic activities were investigated.High efficientβ-Ga₂O₃ photocatalyst was successfully synthesized via alow-temperature hydrothermal method. It is indicated that when the hydrothermaltemperature is 140℃, hydrothermal time is 6h, the initial reactant molar ratio ofgallium nitrate and urea is 1:10, the obtained sample has highest photocatalyticactivity, which is closely concerned with the crystallization, grain size and surfacearea under different grow conditions.The factors of PEG concentration and molecular weight on the photocatalyticproperties ofβ-Ga₂O₃ were investigated in the hydrothermal system and the impactmechanism was deduced. The experimental data showed that when PEG molecularweight was 200, volume dosage was 20mL, the synthesized catalyst exhibited highestphotocatalytic activity. It is proved that suitable PEG concentration and molecularweight can optimize the catalysts morphology, increase the catalysts surface area,produce more oxygen vacancies and gallium-oxygen vacancies, which played anactive role in improving the gas-solid mass transfer rates and suppressing therecombination of photogenerated holes-electrons.The reaction process of VUV photodegradation of toluene and naphthalene byPTR-MS and GC-MS were investigated. A lot of by-products were determinedqualitatively. Some more toxic intermediates such as aldehydes and ketones weredetected. Two kinds of photo-polymer species were discovered in photodegradationnaphthalene at moist air, which were related to the ozone. The possible mechanismsof VUV photodegradation pollutants in different conditions were also proposed.Treatment of single or complex pollutants were further invested by VUV combined withβ-Ga₂O₃(VUV/β-Ga₂O₃) photocatalytic degradation technology. It isconfirmed that VUV/β-Ga₂O₃ technology is more powerful than VUV/TiO₂ todegradate hamful compounds into less harm intermediates. The removal efficiency oftoluene has reached 92.2% in continuous flow reaction. It is testified that thephotocatalytic properties ofβ-Ga₂O₃ is more superior to P25-TiO₂ due to its largerband gap.