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Molecules 2016, 21(4), 532; doi:10.3390/molecules21040532

Identification of Subnanometric Ag Species, Their Interaction with Supports and Role in Catalytic CO Oxidation

1
Departamento de Fisicoquímica de Nanomateriales, Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México (UNAM), Ensenada 22860, Mexico
2
Department of Physical and Analytical Chemistry, Tomsk Polytechnic University, Tomsk 634050, Russia
3
National Research Center “Kurchatov Institute”, Moscow 123182, Russia
4
Departamento de Fisica Aplicada, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada 22860, Mexico
5
Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México (UNAM), México, DF 04510, Mexico
6
CONACYT Research Fellow at Centro de Nanociencias y Nanotecnología, UNAM, Ensenada 22860, Mexico
7
Institute of Catalysis and Petroleumchemistry (ICP), Spanish Council for Scientific Research (CSIC), Madrid 28049, Spain
*
Author to whom correspondence should be addressed.
Academic Editor: Sonia A.C. Carabineiro
Received: 6 February 2016 / Revised: 7 April 2016 / Accepted: 15 April 2016 / Published: 22 April 2016
(This article belongs to the Special Issue Coinage Metal (Copper, Silver, and Gold) Catalysis)
View Full-Text   |   Download PDF [4856 KB, uploaded 22 April 2016]   |  

Abstract

The nature and size of the real active species of nanoparticulated metal supported catalysts is still an unresolved question. The technique of choice to measure particle sizes at the nanoscale, HRTEM, has a practical limit of 1 nm. This work is aimed to identify the catalytic role of subnanometer species and methods to detect and characterize them. In this frame, we investigated the sensitivity to redox pretreatments of Ag/Fe/TiO2, Ag/Mg/TiO2 and Ag/Ce/TiO2 catalysts in CO oxidation. The joint application of HRTEM, SR-XRD, DRS, XPS, EXAFS and XANES methods indicated that most of the silver in all samples is in the form of Ag species with size <1 nm. The differences in catalytic properties and sensitivity to pretreatments, observed for the studied Ag catalysts, could not be explained taking into account only the Ag particles whose size distribution is measured by HRTEM, but may be explained by the presence of the subnanometer Ag species, undetectable by HRTEM, and their interaction with supports. This result highlights their role as active species and the need to take them into account to understand integrally the catalysis by supported nanometals. View Full-Text
Keywords: silver catalysts; subnanometer species; CO oxidation; sensitivity to pretreatments; interaction with support silver catalysts; subnanometer species; CO oxidation; sensitivity to pretreatments; interaction with support
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MDPI and ACS Style

Kotolevich, Y.; Kolobova, E.; Khramov, E.; Cabrera Ortega, J.E.; Farías, M.H.; Zubavichus, Y.; Zanella, R.; Mota-Morales, J.D.; Pestryakov, A.; Bogdanchikova, N.; Cortés Corberán, V. Identification of Subnanometric Ag Species, Their Interaction with Supports and Role in Catalytic CO Oxidation. Molecules 2016, 21, 532.

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