Studies of Supported Ultrafine Pt Particles by Means of Chemisorption and Thermal Desorption
O. A. YAKOVINA, A. S. LISITSYN
Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Pr. Akademika Lavrentyeva 5, Novosibirsk 630090 (Russia)
Keywords: Pt/Оі-AlO, Pt/SiO, наночастицы, нанокластеры, хемосорбция, ТПД, nanoparticles, nanoclusters, chemisorption, TPD
Abstract
Results of chemisorption measurements and experiments on hydrogen thermodesorption carried out with Pt/γ-Al2O3 samples with Pt nanoclusters (size <1 nm) are presented. The reasons of the reversible changes of adsorption properties were studied. The results are compared with the data for platinum nanoparticles (with the size mainly 2-3 nm) deposited on the “inert” oxide (SiO2). The high sensitivity of chemisorption methods and temperature-programmable desorption to the changes in the state of supported metal clusters during thermal treatment of the samples in reducing and neutral media was demonstrated. It was shown that hydrogen adsorption on ultrafine systems is activated, and the adsorption capacity of samples determined from oxygen-hydrogen titration may decrease during multiple titration procedures. A strong effect of Н2О on hydrogen thermodesorption from Pt/γ-Al2O3 samples reduced at high temperature was observed. The obtained results are interpreted taking into account the structural changes of nanoclusters in the low-temperature region and the formation of oxygen vacancies at the metal - support interface under the action of H2 at high temperature.
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