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Published December 28, 2014 | Published
Journal Article Open

Ligand/cluster/support catalytic complexes in heterogeneous ultrananocatalysis: NO oxidation on Ag_3/MgO(100)

Abstract

In the present work we explore via first-principles simulations whether the ligand/cluster/support catalytic complex generated by CO oxidation over silver trimers deposited on the regular MgO(100) surface – i.e. a Ag_3/carbonate or Ag_3(CO_3)/MgO(100) species – can be used as a catalyst in a different reaction: the selective oxidation of NO to NO_2 (or NOox). The Ag_3(CO_3)/MgO(100) complex is first shown to be reasonably stable at room temperature in terms of both disaggregation and sintering, and that it can be generated from Ag3 adsorbed onto an oxygen vacancy defect of the regular MgO(100) surface under oxidation conditions. It is then found that the Ag_3(CO_3)/MgO(100) species transforms under NOox conditions into an even more complex aggregate, a mixed carbonate/double-nitrite Ag_3(CO_3)(NO_2)_2/MgO(100) species, which can then act as an efficient catalyst of NOox. It is noteworthy that under NOox reaction conditions a different ligand/cluster/support catalytic complex is formed with respect to the original COox one. These findings prove the diversity of the catalytic chemistry of subnanometer (or ultranano) metal clusters deposited on oxide substrates, associated with the formation of many different ligand/cluster/support aggregates, the vast amount of combinatorial possibilities thus opening, and the need for computational approaches to perform systematic structural and stoichiometric searches in order to cope with such a multiform diversity.

Additional Information

© 2014 the Owner Societies. Received 16 May 2014, Accepted 07 Aug 2014, First published online 08 Aug 2014. We thank Leonarda Liotta, Prasenjit Sen and Stefan Vajda for stimulating discussions. Financial support from the ERC-AG SEPON project is gratefully acknowledged. Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

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