Role of the Three-Phase Boundary of the Platinum-Support Interface in Catalysis: A Model Catalyst Kinetic Study.
A series of microstructured, supported platinum (Pt) catalyst films (supported on single-crystal yttria-stabilized zirconia) and an appropriate Pt catalyst reference system (supported on single-crystal alumina) were fabricated using pulsed laser deposition and ion-beam etching. The thin films exhibit area-specific lengths of the three-phase boundary (length of three-phase boundary between the Pt, support, and gas phase divided by the superficial area of the sample) that vary over 4 orders of magnitude from 4.5 × 102to 4.9 × 106m m-2, equivalent to structural length scales of 0.2 μm to approximately 9000 μm. The catalyst films have been characterized using X-ray diffraction, atomic force microscopy, high-resolution scanning electron microscopy, and catalytic activity tests employing the carbon monoxide oxidation reaction. When Pt is supported on yttria-stabilized zirconia, the reaction rate clearly depends upon the area-specific length of the three-phase boundary,l(tpb). A similar relationship is not observed when Pt is supported on alumina. We suggest that the presence of the three-phase boundary provides an extra channel of oxygen supply to the Pt through diffusion in or on the yttria-stabilized zirconia support coupled with surface diffusion across the Pt.
School of Chemical Engineering and Advanced Materials, Newcastle University , Merz Court, Newcastle-upon-Tyne NE1 7RU, U.K.
Evangelos I
EI
Papaioannou
Institute for Physical Chemistry, Justus-Liebig-University of Giessen , Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
Christoph
C
Bachmann
Institute for Physical Chemistry, Justus-Liebig-University of Giessen , Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
Jonas J
JJ
Neumeier
School of Chemical Engineering and Advanced Materials, Newcastle University , Merz Court, Newcastle-upon-Tyne NE1 7RU, U.K.
Daniel
D
Frankel
Institute for Physical Chemistry, Justus-Liebig-University of Giessen , Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
Herbert
H
Over
Institute for Physical Chemistry, Justus-Liebig-University of Giessen , Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
Juergen
J
Janek
School of Chemical Engineering and Advanced Materials, Newcastle University , Merz Court, Newcastle-upon-Tyne NE1 7RU, U.K.
Ian S
IS
Metcalfe
carbon monoxide kinetics; model catalysts; patterned catalysts; three-phase boundary
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