Palladium nanowires and nanoparticles in mesoporous silica templates

Nanowires and nanoparticles of palladium are synthesized in mesoporous silicas FSM-16 and HMM-1, and their structural characterization and catalytic performances in CO oxidation have been studied. FSM-16 and HMM-1 were impregnated with H2PdCl4, and the thermal treatment under O2 or N2 atmosphere led to high dispersion of H2PdCl4 into the one-dimensional channels of the mesoporous materials (channel diameter ca. 3 nm). UV-irradiation of the sample in the presence of water and methanol vapors and subsequent H2-reduction resulted in the formation of Pd nanowires with the diameter less than 3 nm and the length up to 300 nm. In contrast, one-step H2-reduction gave Pd nanoparticles in the mesopores. The Pd nanowires and nanoparticles were characterized by means of TEM, XRD, XAFS, and CO uptake. CO oxidation was performed as a test reaction to compare catalytic performances of the Pd nanowires and nanoparticles.