کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10267601 | 459459 | 2005 | 7 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
The wheel-shaped Cu20-tungstophosphate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25â, redox and electrocatalytic properties
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موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
مهندسی شیمی (عمومی)
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چکیده انگلیسی
After prior assessment of its stability by UV-visible spectroscopy, the new complex [Cu20Cl(OH)24(H2O)12(P8W48O184)]25â (Cu20P8W48) was studied by cyclic voltammetry and controlled potential coulometry in pH 0 and pH 5 media. In the two media, the cyclic voltammograms are dominated by the current intensities of processes attributed to the reduction of Cu2+ centers. However, the reduction waves featuring the electrochemical behaviours of the precursor lacunary complex K28Li5[H7P8W48O184] · 92H2O could be tracked down and highlighted. In the pH 0 medium, the first two waves of the lacunary heteropolyanion are practically engulfed in the tail of the overall copper reduction process. A much better separation is obtained in the pH 5 medium and is attributed to the large sensitivity of tungsten centers to pH variations. A simple mixture of the appropriate amounts of copper salt and the lacunary heteropolyanion at room temperature did not allow to reproduce the voltammogram of the pre-synthesized supramolecular species, thus confirming the stability of this complex as a viable entity in solution. Controlled potential coulometry indicates that all the Cu2+ centers within the supramolecular complex remain electroactive. Cyclic voltammograms run at different advancements of the coulometry have permitted gradually a better observation of the W-waves. The supramolecular complex shows a strong catalytic activity towards nitrate and nitrite. Comparison with the activity per copper atom of previously studied copper-substituted heteropolyanions indicates the supramolecular complex to be significantly more efficient, a feature that reinforces the notion that accumulation of transition metals within polyoxometalates should be beneficial for the relevant catalytic processes. This superior efficiency of [Cu20Cl(OH)24(H2O)12(P8W48O184)]25â is due both to the accumulation of Cu-centers and to the more positive potential locations of catalytically active Cu- and W-waves compared to the corresponding waves of other Cu-substituted HPAs.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Electrochemistry Communications - Volume 7, Issue 8, August 2005, Pages 841-847
Journal: Electrochemistry Communications - Volume 7, Issue 8, August 2005, Pages 841-847
نویسندگان
Darine Jabbour, Bineta Keita, Louis Nadjo, Ulrich Kortz, Sib Sankar Mal,