The catalytic properties of thin film Pd-rich GaPd2 in methanol steam reforming

Lukas Mayr, University of Innsbruck
Harald Lorenz, University of Innsbruck
Marc Armbruester, University of Innsbruck
Sebastian Alarcon Villaseca, Max Planck Institute
Yuan Luo, Max Planck Society
Raul Cardoso, Max Planck Society
Ulrich Burkhardt, Max Planck Society
Dmitry Zemlyanov, Purdue University, Birck Nanotechnology Center
Michael Haevecker, Max Planck Society
Raoul Blume, Max Planck Society
Axel Knop-Gericke, Max Planck Society
Bernhard Klotzer, University of Innsbruck
Simon Penner, University of Innsbruck

Date of this Version



An unsupported Pd-rich GaPd2 sample in form of a thin film has been prepared by alternating layer deposition of Pd and Ga metal and was subsequently used as a structurally and chemically stable model system to clarify the catalytic properties of the unsupported intermetallic compound GaPd2 in methanol steam reforming (MSR). The sample revealed a slightly Pd-richer GaPd2 bulk composition of Ga28Pd72, as evidenced by EDX analysis, low-energy ion scattering, X-ray diffraction measurements, and depth profiling by in situ X-ray photoelectron spectroscopy. The latter additionally showed a high stability of GaPd2 both under methanol and oxidative methanol steam reforming conditions. No active redox chemistry of Ga species or other reaction-induced oxidative Ga surface segregation has been detected during catalytic MSR reaction. Corroborating these observations, corresponding catalytic experiments under methanol steam reforming conditions revealed only a, in comparison with elemental Pd, very small activity in methanol dehydrogenation (CO formation rate at maximum 0.019 mbar min(-1); 0.08 site(-1)-s(-1)). Unsupported thin film Pd-rich GaPd2 with the given surface and bulk stoichiometry must therefore be considered a poor methanol steam reforming/dehydrogenation catalyst. In oxidative steam reforming experiments, only total oxidation without significant H-2 formation has been observed. (C) 2013 Elsevier Inc. All rights reserved.


Nanoscience and Nanotechnology