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Title: Synthesis of Colloidal Pd/Au Dilute Alloy Nanocrystals and Their Potential for Selective Catalytic Oxidations

Abstract

Selective oxidations are crucial for the creation of valuable chemical building blocks but often require expensive and unstable stoichiometric oxidants such as hydroperoxides and peracids. To date, many catalysts that contain a single type of active site have not been able to attain the desired level of selectivity for partially oxidized products over total combustion. However, catalysts containing multiple types of active sites have proven to be successful for selective reactions. One category of such catalysts is bimetallic alloys, in which catalytic activity and selectivity can be tuned by modifying the surface composition. Traditional catalyst synthesis methods using impregnation struggle to create catalysts with sufficient control over surface chemistry to accurately tune the ensemble size of the desired active sites. Here in this paper, we describe the synthesis of colloidal nanocrystals of dilute alloys of palladium and gold. We show that when supported on titania (TiO 2), tuning the composition of the Pd/Au nanocrystal surface provides a synergistic effect in the selective oxidation of 2-propanol to acetone in the presence of H 2 and O 2. In particular, we show that certain Pd/Au surface ratios exhibit activity and selectivity far superior to Pd or Au individually. Through precise structural characterizationmore » we demonstrate that isolated atoms of Pd exist in the most active catalysts. The synergy between isolated Pd atoms and Au allows for the formation of reactive oxidizing species, likely hydroperoxide groups, responsible for selective oxidation while limiting oxygen dissociation and, thus, complete combustion. This work opens the way to more efficient utilization of scarce noble metals and new options for catalyzed selective oxidations.« less

Authors:
 [1];  [2];  [1];  [2];  [2]; ORCiD logo [1]
  1. Stanford Univ., CA (United States). Dept. of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1484845
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 40; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Wrasman, Cody J., Boubnov, Alexey, Riscoe, Andrew R., Hoffman, Adam S., Bare, Simon R., and Cargnello, Matteo. Synthesis of Colloidal Pd/Au Dilute Alloy Nanocrystals and Their Potential for Selective Catalytic Oxidations. United States: N. p., 2018. Web. doi:10.1021/jacs.8b07515.
Wrasman, Cody J., Boubnov, Alexey, Riscoe, Andrew R., Hoffman, Adam S., Bare, Simon R., & Cargnello, Matteo. Synthesis of Colloidal Pd/Au Dilute Alloy Nanocrystals and Their Potential for Selective Catalytic Oxidations. United States. doi:10.1021/jacs.8b07515.
Wrasman, Cody J., Boubnov, Alexey, Riscoe, Andrew R., Hoffman, Adam S., Bare, Simon R., and Cargnello, Matteo. Mon . "Synthesis of Colloidal Pd/Au Dilute Alloy Nanocrystals and Their Potential for Selective Catalytic Oxidations". United States. doi:10.1021/jacs.8b07515. https://www.osti.gov/servlets/purl/1484845.
@article{osti_1484845,
title = {Synthesis of Colloidal Pd/Au Dilute Alloy Nanocrystals and Their Potential for Selective Catalytic Oxidations},
author = {Wrasman, Cody J. and Boubnov, Alexey and Riscoe, Andrew R. and Hoffman, Adam S. and Bare, Simon R. and Cargnello, Matteo},
abstractNote = {Selective oxidations are crucial for the creation of valuable chemical building blocks but often require expensive and unstable stoichiometric oxidants such as hydroperoxides and peracids. To date, many catalysts that contain a single type of active site have not been able to attain the desired level of selectivity for partially oxidized products over total combustion. However, catalysts containing multiple types of active sites have proven to be successful for selective reactions. One category of such catalysts is bimetallic alloys, in which catalytic activity and selectivity can be tuned by modifying the surface composition. Traditional catalyst synthesis methods using impregnation struggle to create catalysts with sufficient control over surface chemistry to accurately tune the ensemble size of the desired active sites. Here in this paper, we describe the synthesis of colloidal nanocrystals of dilute alloys of palladium and gold. We show that when supported on titania (TiO2), tuning the composition of the Pd/Au nanocrystal surface provides a synergistic effect in the selective oxidation of 2-propanol to acetone in the presence of H2 and O2. In particular, we show that certain Pd/Au surface ratios exhibit activity and selectivity far superior to Pd or Au individually. Through precise structural characterization we demonstrate that isolated atoms of Pd exist in the most active catalysts. The synergy between isolated Pd atoms and Au allows for the formation of reactive oxidizing species, likely hydroperoxide groups, responsible for selective oxidation while limiting oxygen dissociation and, thus, complete combustion. This work opens the way to more efficient utilization of scarce noble metals and new options for catalyzed selective oxidations.},
doi = {10.1021/jacs.8b07515},
journal = {Journal of the American Chemical Society},
number = 40,
volume = 140,
place = {United States},
year = {2018},
month = {9}
}

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