As one of the priority indoor air pollutants emitted from furnishing and building materials, formaldehyde (HCHO) has attracted a great deal of attention. Long-term exposure to HCHO may result in adverse human health effects and even cancer. Catalytic oxidation of HCHO at room temperature is believed to be an efficient, economic, and environmentally benign technology for indoor HCHO elimination, and the high-efficiency catalyst is the key factor of the above technology. Herein, we have developed two types of high-efficiency manganese dioxide (MnO2) catalysts for HCHO abatement at room temperature. First, we have synthesized ultrathin MnO2 nanosheets with the thickness of 1-2 nm by chemical oxidation of Mn2+ ions in the presence of tetramethylammonium cations in an aqueous solution at room temperature. As-prepared ultrathin MnO2 nanosheets were deposited onto a cheap non-woven fabric made of polyethylene terephthalate (PET). As-synthesized MnO2/PET composite material showed a good activity for HCHO removal at room temperature. And the used MnO2/PET can be simply regenerated by heating at low temperature without any rinse treatment. Based on in-situ DRIFTS and TG-MS studies, the mechanism of HCHO removal and regeneration processes were proposed. Second, we fabricated a 3D-MnO2 framework with the assembly of MnO2 nanosheets and nanowires. The as-resultant 3D-MnO2 can combine a number of excellent structural properties such as interconnected network, low mass density (~7.3 mg cm-3), rich porosity and highly exposed active sites, making it a promising material for catalytic application. Benefited from their quickly reversible and high water content for replenishing the consumed surface hydroxyl groups during HCHO decomposition, and fully exposed active reaction sites, the 3D-MnO2 showed superior activity and stability for HCHO oxidation at room temperature. This is the first finding that inexpensive metal oxides such as 3D-MnO2 can transform ppm-level HCHO into harmless CO2 in as short as sub-second at room temperature. This work also provides new insights into the synthesis of metal oxide-based 3D network materials for air purification.

Manganese dioxide catalyst for airborne formaldehyde oxidation at room temperature

253rd National Meeting (2017)

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