In situ XPS study of methanol reforming on PdGa near-surface intermetallic phases

Christoph Rameshan, University of Innsbruck; Max Planck Society
Werner Stadlmayr, University of Innsbruck
Simon Penner, University of Innsbruck
Harald Lorenz, University of Innsbruck
Lukas Mayr, University of Innsbruck
Michael Haevecker, Max Planck Society
Raoul Blume, Max Planck Society
Tulio Rocha, Max Planck Society
Detre Teschner, Max Planck Society
Axel Knop-Gericke, Max Planck Society
Robert Schlogl, Max Planck Society
Dmitry Zemlyanov, Birck Nanotechnology Center, Purdue University
Norbert Memmel, University of Innsbruck
Bernhard Kloetzer, University of Innsbruck

Date of this Version



Journal of Catalysis Volume 290, June 2012, Pages 126–137


In situ X-ray photoelectron spectroscopy and low-energy ion scattering were used to study the preparation, (thermo)chemical and catalytic properties of 1:1 PdGa intermetallic near-surface phases. Deposition of several multilayers of Ga metal and subsequent annealing to 503-523 K led to the formation of a multi-layered 1:1 PdGa near-surface state without desorption of excess Ga to the gas phase. In general, the composition of the PdGa model system is much more variable than that of its PdZn counterpart, which results in gradual changes of the near-surface composition with increasing annealing or reaction temperature. In contrast to near-surface PdZn, in methanol steam reforming, no temperature region with pronounced CO2 selectivity was observed, which is due to the inability of purely intermetallic PdGa to efficiently activate water. This allows to pinpoint the water-activating role of the intermetallic/support interface and/or of the oxide support in the related supported PdxGa/Ga2O3 systems, which exhibit high CO2 selectivity in a broad temperature range. In contrast, corresponding experiments starting on the purely bimetallic model surface in oxidative methanol reforming yielded high CO2 selectivity already at low temperatures (similar to 460 K), which is due to efficient O-2 activation on PdGa. In situ detected partial and reversible oxidative Ga segregation on intermetallic PdGa is associated with total oxidation of intermediate C-1 oxygenates to CO2. (c) 2012 Elsevier Inc. All rights reserved.


Nanoscience and Nanotechnology