(152c) Spectroscopic Identification of Intermediates In Aqueous-Phase Oxidation of Glycerol Over Au

Effective in situ and/or operando techniques in which to monitor reactions and identify surface transformations have long been a challenge to obtain. Even more challenging is the characterization of aqueous-phase reactions by conventional techniques, such as EELS or IR spectroscopies, wherein the former necessarily requires a vacuum environment, and the latter suffers from the large water background. With the recent increased interest in aqueous phase conversions there is clearly a need for a surface-selective spectroscopy capable of analyzing catalysts in their actual operating environments.

Of particular interest is glycerol oxidation in basic solution. Glycerol is a main byproduct in biofuels production, and its conversion to useful chemicals is desirable. Though mechanisms for its transformation have been proposed, many proposed intermediates have yet to be detected via common mass spectrometry techniques. Additionally, little work has been done on the prediction of surface intermediaries.

In this study, we report the in situ time-resolved identification of adsorbates and reaction intermediates in the basic aqueous-phase oxidation reaction of glycerol via surface-enhanced Raman spectroscopy (SERS) over Au nanoshells (NS's), submicron-sized gold-shell/silica-core spheres that enhance Raman signals of adsorbed species. Coupled with batch experiments using a Au/C catalyst, we gain important insights into the effect of pH and other parameters on the surface reaction.