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Near-Ambient-Pressure X-ray Photoelectron Spectroscopy Study of Methane-Induced Carbon Deposition on Clean and Copper-Modified Polycrystalline Nickel Materials

MPS-Authors
http://pubman.mpdl.mpg.de/cone/persons/resource/persons130740

Rameshan,  Raffael
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;
Institute of Physical Chemistry, University of Innsbruck;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons21743

Knop-Gericke,  Axel
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons21590

Hävecker,  Michael
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons21378

Blume,  Raoul
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons22071

Schlögl,  Robert
Inorganic Chemistry, Fritz Haber Institute, Max Planck Society;

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jp5b07317 1..11 - acs.jpcc.pdf
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Citation

Rameshan, R., Mayr, L., Klötzer, B., Eder, D., Knop-Gericke, A., Hävecker, M., et al. (2015). Near-Ambient-Pressure X-ray Photoelectron Spectroscopy Study of Methane-Induced Carbon Deposition on Clean and Copper-Modified Polycrystalline Nickel Materials. The Journal of Physical Chemistry C, 119(48), 26948-26958. doi:10.1021/acs.jpcc.5b07317.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0029-1966-1
Abstract
In order to simulate solid-oxide fuel cell (SOFC)-related coking mechanisms of Ni, methane-induced surface carbide and carbon growth was studied under close-to-real conditions by synchrotron-based near-ambient-pressure (NAP) X-ray photoelectron spectroscopy (XPS) in the temperature region between 250 and 600 °C. Two complementary polycrystalline Ni samples were used, namely, Ni foam—serving as a model structure for bulk Ni in cermet materials such as Ni/YSZ—and Ni foil. The growth mechanism of graphene/graphite species was found to be closely related to that previously described for ethylene-induced graphene growth on Ni(111). After a sufficiently long “incubation” period of the Ni foam in methane at 0.2 mbar and temperatures around 400 °C, cooling down to ∼250 °C, and keeping the sample at this temperature for 50–60 min, initial formation of a near-surface carbide phase was observed, which exhibited the same spectroscopic fingerprint as the C2H4 induced Ni2C phase on Ni(111). Only in the presence of this carbidic species, subsequent graphene/graphite nucleation and growth was observed. Vice versa, the absence of this species excluded further graphene/graphite formation. At temperatures above 400 °C, decomposition/bulk dissolution of the graphene/graphite phase was observed on the rather “open” surface of the Ni foam. In contrast, Ni foil showed—under otherwise identical conditions—predominant formation of unreactive amorphous carbon, which can only be removed at ≥500 °C by oxidative clean-off. Moreover, the complete suppression of carbide and subsequent graphene/graphite formation by Cu-alloying of the Ni foam and by addition of water to the methane atmosphere was verified.