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Title: Beating Heterogeneity of Single-Site Catalysts: MgO-Supported Iridium Complexes

Abstract

Catalysts consisting of isolated metal atoms on oxide supports have attracted wide attention because they offer unique catalytic properties, but their structures remain largely unknown because the metals are bonded at various, heterogeneous surface sites. Now, by using highly crystalline MgO as a support for metal sites made from a mononuclear organoiridium precursor and investigating the surface species with X-ray absorption spectroscopy, atomic resolution electron microscopy, and electronic structure theory, we have differentiated among the MgO surface sites for iridium bonding. The results demonstrate the contrasting structures and catalytic properties of samples, even including those incorporating iridium at loadings as low as 0.01 wt % and showing that the latter are nearly ideal in the sense of having almost all the Ir atoms at equivalent surface sites, with each Ir atom bonded to three oxygen atoms of the MgO surface. These supported molecular catalysts are modeled accurately with density functional theory. The results open the door to the precise synthesis of families of single-site catalysts. The work was supported by the U.S. Department of Energy (DOE), Office of Science (SC), Basic Energy Sciences (BES), Grant DE-FG02-04ER15513 and the DOE BES Catalysis Center Program by a subcontract from Pacific Northwest Nationalmore » Laboratory (KC0301050-47319) to the University of Alabama. We thank Chevron for fellowship support of ASH and LMD. DAD thanks the Robert Ramsay Chair Fund of The University of Alabama for support. A portion of the research was performed using facilities of the Environmental Molecular Sciences Laboratory (Ringgold ID 130367), a DOE SC User Facility sponsored by the Office of Biological and Environmental Research. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by DOE SC BES under Contract No. DE-AC02- 76SF00515. We thank Chevron Energy Technology Company for performing the XRD experiments.« less

Authors:
 [1]; ORCiD logo [1];  [2];  [1];  [3];  [3];  [4]; ORCiD logo [2]; ORCiD logo [1]
  1. Department of Chemical Engineering, University of California—Davis, Davis, California 95616, United States
  2. Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, United States
  3. Department of Chemical Engineering, University of California—Davis, Davis, California 95616, United States; Department of Materials Science and Engineering, University of California—Davis, Davis, California 95616, United States
  4. Fundamental and Computational Sciences Directorate, Institute for Integrated Catalysis and Environmental Molecular Science Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1495402
Report Number(s):
PNNL-SA-136772
Journal ID: ISSN 2155-5435
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 8; Journal Issue: 4; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
single-site catalyst, iridium catalyst, MgO-supported catalyst, surface heterogeneity, metal-support interaction, electron microscopy, EXAFS spectroscopy, IR spectroscopy

Citation Formats

Hoffman, Adam S., Debefve, Louise M., Zhang, Shengjie, Perez-Aguilar, Jorge E., Conley, Edward T., Justl, Kimberly R., Arslan, Ilke, Dixon, David A., and Gates, Bruce C. Beating Heterogeneity of Single-Site Catalysts: MgO-Supported Iridium Complexes. United States: N. p., 2018. Web. doi:10.1021/acscatal.8b00143.
Hoffman, Adam S., Debefve, Louise M., Zhang, Shengjie, Perez-Aguilar, Jorge E., Conley, Edward T., Justl, Kimberly R., Arslan, Ilke, Dixon, David A., & Gates, Bruce C. Beating Heterogeneity of Single-Site Catalysts: MgO-Supported Iridium Complexes. United States. https://doi.org/10.1021/acscatal.8b00143
Hoffman, Adam S., Debefve, Louise M., Zhang, Shengjie, Perez-Aguilar, Jorge E., Conley, Edward T., Justl, Kimberly R., Arslan, Ilke, Dixon, David A., and Gates, Bruce C. 2018. "Beating Heterogeneity of Single-Site Catalysts: MgO-Supported Iridium Complexes". United States. https://doi.org/10.1021/acscatal.8b00143.
@article{osti_1495402,
title = {Beating Heterogeneity of Single-Site Catalysts: MgO-Supported Iridium Complexes},
author = {Hoffman, Adam S. and Debefve, Louise M. and Zhang, Shengjie and Perez-Aguilar, Jorge E. and Conley, Edward T. and Justl, Kimberly R. and Arslan, Ilke and Dixon, David A. and Gates, Bruce C.},
abstractNote = {Catalysts consisting of isolated metal atoms on oxide supports have attracted wide attention because they offer unique catalytic properties, but their structures remain largely unknown because the metals are bonded at various, heterogeneous surface sites. Now, by using highly crystalline MgO as a support for metal sites made from a mononuclear organoiridium precursor and investigating the surface species with X-ray absorption spectroscopy, atomic resolution electron microscopy, and electronic structure theory, we have differentiated among the MgO surface sites for iridium bonding. The results demonstrate the contrasting structures and catalytic properties of samples, even including those incorporating iridium at loadings as low as 0.01 wt % and showing that the latter are nearly ideal in the sense of having almost all the Ir atoms at equivalent surface sites, with each Ir atom bonded to three oxygen atoms of the MgO surface. These supported molecular catalysts are modeled accurately with density functional theory. The results open the door to the precise synthesis of families of single-site catalysts. The work was supported by the U.S. Department of Energy (DOE), Office of Science (SC), Basic Energy Sciences (BES), Grant DE-FG02-04ER15513 and the DOE BES Catalysis Center Program by a subcontract from Pacific Northwest National Laboratory (KC0301050-47319) to the University of Alabama. We thank Chevron for fellowship support of ASH and LMD. DAD thanks the Robert Ramsay Chair Fund of The University of Alabama for support. A portion of the research was performed using facilities of the Environmental Molecular Sciences Laboratory (Ringgold ID 130367), a DOE SC User Facility sponsored by the Office of Biological and Environmental Research. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by DOE SC BES under Contract No. DE-AC02- 76SF00515. We thank Chevron Energy Technology Company for performing the XRD experiments.},
doi = {10.1021/acscatal.8b00143},
url = {https://www.osti.gov/biblio/1495402}, journal = {ACS Catalysis},
issn = {2155-5435},
number = 4,
volume = 8,
place = {United States},
year = {2018},
month = {3}
}