科研之友
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摘要
The origin of oxidation activity of gold catalysts has been a subject of great interest, particularly with the discovery of selective glycerol oxidation under water-phase alkaline conditions, for which neither small gold nanoparticles nor a catalyst support is necessary for activity. Little is known about the interactions among the catalyst surface, reactant, and hydroxyl species, which have never been examined spectroscopically because of a lack of developed in situ methods. In this work, we studied the room-temperature, water-phase reaction of glycerol oxidation using gold nanoshells (Au NSs), in which the gold substrate was active for surface-enhanced Raman spectroscopy (SERS) and catalysis. Analysis of glycerol solutions at high pH values and with oxygen content indicated that glycerol and glycerolate species did not bind directly to the catalyst surface in the absence of oxygen. However, glycerate surface species formed very rapidly when oxygen was present, suggesting an Eley-Rideal-type reaction mechanism with O-2 (and/or O-2-activated OH-) as the adsorbed species. SERS analysis of carbon monoxide chemisorption on Au NSs indicated that higher pH values progressively weakened the C-O bond as the Au negative charge increased. The importance of high alkalinity to Au-catalyzed alcohol oxidation may result from both the activation of glycerol via deprotonation and the weakening of the adsorbed O-2 double bond via induced Au negative charge.
- 出版日期2013-11
