FIZIKA A 4 (1995) 2, 181-189

RHEED AND TPD STUDIES OF THE EFFECT OF PARTICLE SIZE ON CO DESORPTION FROM Al₂O₃ SUPPORTED Pd AND Rh MODEL CATALYSTS

VLADIMIR MATOLIN
Department of Electronics and Vacuum Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic

Received 7 April 1995
Revised manuscript received 6 July 1995

Transition metals in form of small supported particles are frequently used in heterogeneous catalytic reactions. One point of actual interest concerns the reactivity of low co-ordination sites characteristic for particle surface. The non continuous epitaxial layers of Pd and Rh were grown on insulator substrates (Al₂O₃) by molecular beam epitaxy. The reflection high energy electron diffraction (RHEED) offered a readily applicable method for in-situ observation of epitaxial layer growth. As a model reaction CO adsorption was studied by means of the temperature programmed desorption (TPD) using a differentially pumped mass spectrometer with a molecular beam doser. It was shown that the activation energy of CO desorption decreases with decreasing particle size.

UDC 538.971
PACS 68.45.Da, 68.55.Bd

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