Metal additives can greatly improve the catalytic oxidation of photocatalysts for degrading volatile organic compounds (VOCs) including formaldehyde. Different type metal, including Pd, Cu and Na, were doped in TiO 2 (B) nanosheets with oxygen vacancy, and the degradation rate of HCHO were evaluated using the above catalysts. A series of theoretical and experimental studies on these modified TiO 2 (B) photocatalysts were carried out. The presence of O v leads to the appearance of impurity levels under the conduction band of TiO 2 (B), which could enhance the absorption in the visible spectral range by reducing the band gap and inhibiting the recombination of photo-induced charges. TiO 2 (B) with oxygen vacancies and doped with Na is used as a photocatalyst for degrading HCHO, and the removal rate up to 80% within 50 min. It is quite important to match the bandgap structure of photocatalysts and redox potential of O 2 /•O 2 − . Doping of excessive metals is detrimental to the separation and transfer of photogenerated charges. The intermediates and mechanism of photocatalytic oxidation of HCHO were investigated by in situ DRIFTS.
Shaopeng Rong,Pengyi Zhang,Yajie Yang,Lin Zhu,Jinlong Wang,Fang Liu
Formaldehyde (HCHO) causes increasing concerns, because of its ubiquitous presence in the indoor environment and its irritating and carcinogenic nature, with regard to humans. The fast abatement of HCHO is of significant practical interest at room temperature. In this paper, we fabricate a three-dimensional manganese dioxide framework (3D-MnO2), which has interconnected network structures, low mass density (∼7.3 mg cm–3), and high absorption capacity for organic liquids. In particular, the 3D-MnO2 showed excellent activity and stability for HCHO oxidation at room temperature, achieving 45% of 100 ppm of HCHO mineralized into CO2 under high gas hourly space velocity (GHSV = 180 L gcat–1 h–1). The excellent performance of 3D-MnO2 catalysts in decomposing HCHO can be ascribed to their quick reversibility and high water content for replenishing the consumed surface hydroxyl groups during HCHO decomposition, and fully exposed active reaction sites. It is valuable to know that inexpensive metal oxides such as MnO2 can transform ppm-level HCHO into harmless CO2 in a timeframe as brief as a subsecond at room temperature.
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