Nanostructured H(3+x)PW(12-x)Nb(x)O(40) (x=0-3) Keggin Heteropolyacid Catalysts

作者：Choi Jung Ho; Park Dong Ryul; Park Sunyoung; Song In Kyu^*

来源：Journal of Nanoscience and Nanotechnology, 2011, 11(9): 7870-7875.

DOI：10.1166/jnn.2011.4711

• Keggin Heteropolyacid Nanocatalysts
• Scanning Tunneling Microscopy
• Tunneling Spectroscopy
• Heteropolyacid
• Negative Differential Resistance
• Redox Property

Nanostructured H(3+x)PW(12-x)Nb(x)O(40) (x = 0, 1, 2, 3) Keggin heteropolyacid (HPA) catalysts were investigated by scanning tunneling microscopy (STM) and tunneling spectroscopy to probe their redox property and oxidation catalysis. STM image showed that the HPAs formed two-dimensional well-ordered monolayer arrays on graphite surface. In tunneling spectra of the HPAs deposited on graphite, they exhibited a distinctive current voltage behavior referred to as negative differential resistance (NDR). NOR peak voltage measured atop HPA molecule was then correlated with reduction potential and absorption edge energy determined by electrochemical method and UV-visible spectroscopy, respectively. It was revealed that NOR peak voltage of the HPAs appeared at less negative voltage with increasing reduction potential and with decreasing absorption edge energy. In order to correlate NDR peak voltage of H(3+x)PW(12-x)Nb(x)O(40) Keggin HPAs with oxidation catalysis, oxidative dehydrogenation of isobutyraldehyde to methacrolein was carried out as a model reaction. NOR peak voltage of the HPAs appeared at less negative voltage with increasing yield for methacrolein.

• 出版日期2011-9