Manganese Oxide Nanoarchitectures as Broad-Spectrum Sorbents for Toxic Gases

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• 作者：Jeffrey W. Long ; Jean M. Wallace ; Gregory W. Peterson ; Kim Huynh
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：January 20, 2016
• 年：2016
• 卷：8
• 期：2
• 页码：1184-1193
• 全文大小：723K
• ISSN：1944-8252

文摘

We demonstrate that sol–gel-derived manganese oxide (MnOx) nanoarchitectures exhibit broad-spectrum filtration activity for three chemically diverse toxic gases: NH₃, SO₂, and H₂S. Manganese oxides are synthesized via the reaction of NaMnO₄ and fumaric acid to form monolithic gels of disordered, mixed-valent Na-MnOx; incorporated Na⁺ is readily exchanged for H⁺ by subsequent acid rinsing to form a more crystalline H-MnOx phase. For both Na-MnOx and H-MnOx forms, controlled pore-fluid removal yields either densified, yet still mesoporous, xerogels or low-density aerogels (prepared by drying from supercritical CO₂). The performance of these MnOx nanoarchitectures as filtration media is assessed using dynamic-challenge microbreakthrough protocols. We observe technologically relevant sorption capacities under both dry conditions and wet (80% relative humidity) for each of the three toxic industrial chemicals investigated. The Na-MnOx xerogels and aerogels provide optimal performance with the aerogel exhibiting maximum sorption capacities of 39, 200, and 680 mg g^–1 for NH₃, SO₂, and H₂S, respectively. Postbreakthrough characterization using X-ray photoelectron spectroscopy (XPS) and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms that NH₃ is captured and partially protonated within the MnOx structure, while SO₂ undergoes oxidation by the redox-active oxide to form adsorbed sulfate at the MnOx surface. Hydrogen sulfide is also oxidized to form a combination of sulfate and sulfur/polysulfide products, concomitant with a decrease in the average Mn oxidation state from 3.43 to 2.94 and generation of a MnOOH phase.