TY - JOUR
T1 - On the nature of the active state of supported ruthenium catalysts used for the oxidation of carbon monoxide
T2 - Steady-state and transient kinetics combined with in situ infrared spectroscopy
AU - Assmann, Jens
AU - Narkhede, Vijay
AU - Khodeir, Lamma
AU - Löffler, Elke
AU - Hinrichsen, Olaf
AU - Birkner, Alexander
AU - Over, Herbert
AU - Muhler, Martin
PY - 2004/9/23
Y1 - 2004/9/23
N2 - The oxidation of CO over Ru/MgO and Ru/SiO2 catalysts was used as a simple model reaction to derive turnover frequencies at atmospheric pressure, which were observed to agree with kinetic data obtained under high-vacuum conditions with supported ruthenium catalysts and the RuO 2(110) single-crystal surface. Thus, it was possible to bridge both the pressure and the materials gap. However, a partial deactivation was observed initially, which was identified as an activated process, both under net reducing and net oxidizing conditions. Temperature-programmed reduction (TPR) experiments were performed subsequently in the same reactor, to monitor the degree of oxidation, as a function of the reaction temperature and the CO/O 2 reactant feed ratio. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, the structural changes of the ruthenium catalysts during the oxidation of CO were confirmed, under relevant reaction conditions. Under net reducing conditions, only domains of RuO2 seem to exist on the metallic ruthenium particles, whereas, under net oxidizing conditions, the ruthenium particles were fully oxidized to bulk RuO2 particles, which may expose less-active facets, such as the RuO2(100)-c(2 × 2) surface.
AB - The oxidation of CO over Ru/MgO and Ru/SiO2 catalysts was used as a simple model reaction to derive turnover frequencies at atmospheric pressure, which were observed to agree with kinetic data obtained under high-vacuum conditions with supported ruthenium catalysts and the RuO 2(110) single-crystal surface. Thus, it was possible to bridge both the pressure and the materials gap. However, a partial deactivation was observed initially, which was identified as an activated process, both under net reducing and net oxidizing conditions. Temperature-programmed reduction (TPR) experiments were performed subsequently in the same reactor, to monitor the degree of oxidation, as a function of the reaction temperature and the CO/O 2 reactant feed ratio. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, the structural changes of the ruthenium catalysts during the oxidation of CO were confirmed, under relevant reaction conditions. Under net reducing conditions, only domains of RuO2 seem to exist on the metallic ruthenium particles, whereas, under net oxidizing conditions, the ruthenium particles were fully oxidized to bulk RuO2 particles, which may expose less-active facets, such as the RuO2(100)-c(2 × 2) surface.
UR - http://www.scopus.com/inward/record.url?scp=4944226758&partnerID=8YFLogxK
U2 - 10.1021/jp0401675
DO - 10.1021/jp0401675
M3 - Article
AN - SCOPUS:4944226758
SN - 1520-6106
VL - 108
SP - 14634
EP - 14642
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 38
ER -