Effect of carboxylic acid salts on the syntheses of Pt/MWNTs for nitrobenzene hydrogenation

Platinum nanoparticles supported on carbon nanotubes are attracting much interest owning to their unique catalytic, hydrogen storage and electrical characteristics. There are many methods for the loading of platinum nanoparticles on carbon nanotubes includes dispersing a solution or suspension of solid support and reducing the metal atoms to activate the catalyst. Most popular methods were known by adding reducing agents such as HCHO, HCOOH, NaBH4, and N2H4[1]. Electrostatic stabilization is an alternative method of obtaining colloidal metal particle dispersion in solution. The acetate and citrate has been used as stabilizer to prepare metal nanoparticles such as Au, Pd. Ag and Pt.In this work a new method of synthesis of highly dispersed Pt nanoparticles with large catalytic surface area on multi-walled carbon nanotubes in low temperatures and short times under high-intensity ultrasonic field was developed. A variety of Pt/MWNTs catalysts were prepared from an alcoholic solution of H2PtCl6 in the presence of carbon nanotube by adding a small amount of acetate salts as stabilizer and dispersant. In the process the alcoholic solution containing the metal salt in the presence of acetate ions is refluxed at K to decompose 2-propanole to yield in situ generated reducing species for the reduction of the platinum ions to their elemental states. The H2PtCl6 solution became colorless from brown with Pt deposition. Fig. 1 shows the X-ray diffraction patterns for the prepared catalysts (7 to 11). In all cases, the peaks observed indicate the presence of the face-centred cubic structure typical of platinum metal, represented by the crystalline planes (111), (200), (220), and also some reflections characteristics of carbon nanotubes identified as C (002).As shown in Fig. 1the broader diffraction peaks for the four catalysts (8,9,10 and 11) led to smaller average particle size as calculated by the Scherrer equation.