Cyclic Voltammetry as a Potential Predictive Method for Supported Nanocrystalline Gold Catalysts for Oxidation in Aqueous Media

摘要

Nanocrystalline supported Au is a potent catalyst for oxidation of alcohols and polyols in aqueous media using oxygen in which exclusive formation of the mono-acid can be observed. However, relatively non-selective catalysts for the same reaction can also be prepared. Herein we present a detailed characterization study of wholly selective and non-selective Au/graphite catalysts used in the oxidation of glycerol to glyceric acid using a combination of cyclic voltammetry (CV) and transmission electron microscopy (TEM). Analysis using TEM, a technique that is often incisive with supported Au catalysts, in this particular case shows that the non-selective catalysts comprise relatively larger Au crystallites as compared to those of the more selective catalysts. In addition, a set of three Au/C with different selectivities for glyceric acid were characterized using TEM but no discernable differences were observed which could be correlated with the selectivity differences. A detailed study using CV shows distinct differences between the four catalysts. In particular, differences in the activity and selectivity of these Au/graphite catalysts towards glycerol oxidation can be correlated to differences in the relative rates of formation of the selective oxygen species and surface poisons as determined using cyclic voltammetry. It is considered that these cyclic voltammetry correlations can have predictive potential for supported Au catalysts.