The size effect in the catalytic activity of AgcorePt shell nanoparticles

It has been shown that, in the presence of 6.3-nm silver nanoparticles, platinum is reduced in a K2PtCl4-containing aqueous solution after it is saturated with hydrogen. The process yields bimetallic AgcorePtshell “core/shell” nanoparticles. Nanoparticles have been synthesized with different silver-to-platinum molar ratios from 9: 1 to 1: 9. Optical spectroscopy, electron microscopy, and electron diffraction data have confirmed the formation of the core/shell nanoparticles. Bimetallic AgcorePtshell nanoparticles exhibit the ability to catalyze the reduction of methyl viologen with hydrogen in an alkaline aqueous solution, which is typical of platinum nanoparticles. The existence of a “critical” thickness of the platinum shell below which the catalytic reduction of methyl viologen does not take place has been established. The critical thickness is about 1 nm, which corresponds to approximately two atomic platinum layers on a silver core.