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Combination of Density Functional Theory and Microkinetic Study to the Mn-Doped CeO2 Catalysts for CO Oxidation: A Case Study to Understand the Doping Metal Content
journal contribution
posted on 2018-10-18, 00:00 authored by Weiyu Song, Lulu Chen, Jianlin Deng, Meizan Jing, Huiling Zheng, Jian Liu, Zhen ZhaoCeO2 doped
with metal is employed in many catalytic
reactions. Optimizing the content of metal is a routine step to improve
the activity. In low doping metal content, the catalytic performance
improves with the increase of the doping metal content. However, the
catalytic performance decreases beyond the optimal doping metal content.
To our best knowledge, the molecular level understanding to such phenomenon
has never been reached. In the present study, Mn-doped CeO2 for CO oxidation has been taken as a case study toward this aim.
Three different models, in which one, two, and three Mn atoms replace
Ce atoms in CeO2(111) 3 × 3 supercell, were constructed.
The oxidation state for all Mn atoms is +3. Because of charge imbalance,
O22– and O2– species would form spontaneously via a combination of lattice O
on Mn2Cex–2O2x(111) and Mn3Cex–3O2x(111) surface, respectively.
On all these three surfaces, CO oxidation follows the MvK mechanism
which involves lattice oxygen atom. The main steps include CO physisorption,
CO chemisorption, the formation and desorption of CO2,
O2 adsorption, a second CO adsorption and the reaction
between CO and adsorbed O2–. Microkinetics
simulations show that CO oxidation rates and optimal temperatures
are different for these three surfaces. Optimal temperatures for CO
oxidation depend on oxygen adsorption energy. The CO oxidation rate
is highly influenced by the adsorption energy of the second CO molecule.
This work provides insights into the influence of different Mn doping
on the catalytic performance of CeO2.