Enhanced Hydrogenation Properties of Size Selected Pd-C Core-Shell Nanoparticles; Effect of Carbon Shell Thickness

Abstract

Effect of nanoparticle size and alloying has been well studied in Pd and Pd alloy nanoparticles and explained on the basis of modifications in the crystal structure and Pd 4d binding energy position. In the present study, the effect of carbon shell thickness on the hydrogenation properties of gas phase synthesized Pd-C core shell nanoparticles having controllable nanoparticle core and shell thickness has been investigated. A large improvement in H/Pd ratio and increased hydrogen induced lattice expansion is observed in Pd-C nanoparticles. These results are explained on the basis of lowering of coordination number of Pd surface sites at Pd-C core shell interface revealed by the increase in the Pd 4d binding energy on increase in shell thickness. By combining the modification in electronic properties due to the size and the alloying effects with that due to carbon shell thickness, as reported in the present study, Pd-H interaction can be significantly enhanced.