No abstract

Preferential oxidation (PROX) of CO is an important practical process to purify H2 for use in polymer electrolyte fuel cells. Although many supported noble metal catalysts have been reported so far, their catalytic performances remain insufficient for operation at low temperature. We found that Pt nanoparticles in mesoporous silica give unprecedented activity, selectivity, and durability in the PROX reaction below 353 K. We also studied the promotional effect of mesoporous silica in the Pt-catalyzed PROX reaction by infrared spectroscopy using the isotopic tracer technique. Gas-phase O2 is not directly used for CO oxidation, but the oxygen of mesoporous silica is incorporated into CO2. These results suggest that CO oxidation is promoted by the attack of the surface OH groups to CO on Pt without forming water.

Mesoporous silica films work as templates to form uniform nanoparticles of Au and Pt. The composite materials form an array of metal nanoparticles (diameter ca. 2.5 nm) in the one-dimensional mesopores (pore diameter 2.7 nm), showing an ordered structure in the TEM observation. The nanoparticles are isolated from the silica film by dissolving with a diluted HF solution, and in the presence of 1-dodecanethiol unsupported Au nanoparticles form a superlattice structure.