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Counting of Oxygen Defects versus Metal Surface Sites in Methanol Synthesis Catalysts by Different Probe Molecules
Author(s) -
Fichtl Matthias B.,
Schumann Julia,
Kasatkin Igor,
Jacobsen Nikolas,
Behrens Malte,
Schlögl Robert,
Muhler Martin,
Hinrichsen Olaf
Publication year - 2014
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201400575
Subject(s) - catalysis , chemisorption , methanol , adsorption , oxygen , desorption , chemistry , molecule , metal , heterogeneous catalysis , inorganic chemistry , analytical chemistry (journal) , organic chemistry
Different surface sites of solid catalysts are usually quantified by dedicated chemisorption techniques from the adsorption capacity of probe molecules, assuming they specifically react with unique sites. In case of methanol synthesis catalysts, the Cu surface area is one of the crucial parameters in catalyst design and was for over 25 years commonly determined using diluted N 2 O. To disentangle the influence of the catalyst components, different model catalysts were prepared and characterized using N 2 O, temperature programmed desorption of H 2 , and kinetic experiments. The presence of ZnO dramatically influences the N 2 O measurements. This effect can be explained by the presence of oxygen defect sites that are generated at the Cu‐ZnO interface and can be used to easily quantify the intensity of Cu‐Zn interaction. N 2 O in fact probes the Cu surface plus the oxygen vacancies, whereas the exposed Cu surface area can be accurately determined by H 2 .