Controlling metal particle size in preparation of Pd/SiO2 catalysts

Palladium nanoparticles have been fabricated on Aerosil 200 support using (i) "Controlled Colloidal Synthesis", (ii) PDDA stabilized Pd sol (both liquid phase reduction with ethanol) and (iii) incipient wetness method (as reference). Oxidation/reduction treatment was employed to remove the carbonaceous impurities from the samples during which no change in the particle size was experienced, However, the turnover frequency referred to Pd surface exposed significantly changed and FTIR technique, was used to monitor the alteration of Pd surface by means of CO chemisorption. It turned out that after treatment the distribution of the overlapping stretching band system of the prevailing bridge CO forms was changed indicating either a change in the face orientation of Pd crystallites, or formation of clean Pd faces in oxidation/reduction process.