Preparation of carbon-supported Pd and Au-Pd catalysts via optimized adsorption of metallic complexes

A series of Pd/C and Au-Pd/C catalysts were prepared in an optimized and controlled adsorption fashion, by determining the point of zero-charge (PZC) of the carbon support and the nature of metal species present in solution over the whole pH range. In the case of the monometallic Pd/C samples, these two parameters influence the adsorption of metallic species on the support as function of the pH, which might be explained in terms of electrostatic interactions. In the case of gold, maximum adsorption occurs over the whole pH range but the Au/C ratios measured by XPS could be maximized in a certain pH-window. These catalysts are highly active in glyoxal oxidation and XPS characterization demonstrated that the activity is correlated with Pd/C ratios above a threshold value and with an important degree of Pd reduction.