Tremendous Effect of the Morphology of Birnessite-Type Manganese Oxide Nanostructures on Catalytic Activity

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• 作者：Jingtao Hou ; Yuanzhi Li ; Mingyang Mao ; Lu Ren ; Xiujian Zhao
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：September 10, 2014
• 年：2014
• 卷：6
• 期：17
• 页码：14981-14987
• 全文大小：419K
• ISSN：1944-8252

文摘

The octahedral layered birnessite-type manganese oxide (OL-1) with the morphologies of nanoflowers, nanowires, and nanosheets were prepared and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric/differential scanning calorimetry (TG/DSC), Brunnauer鈥揈mmett鈥揟eller (BET), inductively coupled plasma (ICP), and X-ray photoelectron spectroscopy (XPS). The OL-1 nanoflowers possess the highest concentration of oxygen vacancies or Mn³⁺, followed by the OL-1 nanowires and nanosheets. The result of catalytic tests shows that the OL-1 nanoflowers exhibit a tremendous enhancement in the catalytic activity for benzene oxidation as compared to the OL-1 nanowires and nanosheets. Compared to the OL-1 nanosheets, the OL-1 nanoflowers demonstrate an enormous decrease (螖T₅₀ = 274 掳C; 螖T₉₀ > 248 掳C) in reaction temperatures T₅₀ and T₉₀ (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation. The origin of the tremendous effect of morphology on the catalytic activity for the nanostructured OL-1 catalysts is experimentally and theoretically studied via CO temperature-programmed reduction (CO-TPR) and density functional theory (DFT) calculation. The tremendous catalytic enhancement of the OL-1 nanoflowers compared to the OL-1 nanowires and nanosheets is attributed to their highest surface area as well as their highest lattice oxygen reactivity due to their higher concentration of oxygen vacancies or Mn³⁺, thus tremendously improving the catalytic activity for the benzene oxidation.

Keywords:

catalytic; manganese oxide; morphology effect; oxygen vacancy