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Title: Uniform Pt/Pd Bimetallic Nanocrystals Demonstrate Platinum Effect on Palladium Methane Combustion Activity and Stability

Abstract

Bimetallic catalytic materials are in widespread use for numerous reactions, as the properties of a monometallic catalyst are often improved upon addition of a second metal. In studies with bimetallic catalysts, it remains challenging to establish clear structure–property relationships using traditional impregnation techniques, due to the presence of multiple coexisting active phases of different sizes, shapes, and compositions. Here, a convenient approach to prepare small and uniform Pt/Pd bimetallic nanocrystals with tailorable composition is demonstrated, despite the metals being immiscible in the bulk. By depositing this set of controlled nanocrystals onto a high-surface-area alumina support, we systematically investigate the effect of adding platinum to palladium catalysts for methane combustion. At low temperatures and in the absence of steam, all bimetallic catalysts show activity nearly identical with that of Pt/Al 2O 3, with much lower rates in comparison to that of the Pd/Al 2O 3 sample. BUt, unlike Pd/Al 2O 3, which experiences severe low-temperature steam poisoning, all Pt/Pd bimetallic catalysts maintain combustion activity on exposure to excess steam. These features are due to the influence of Pt on the Pd oxidation state, which prevents the formation of a bulk-type PdO phase. Despite lower initial combustion rates, hydrothermal aging of themore » Pd-rich bimetallic catalyst induces segregation of a PdO phase in close contact to a Pd/Pt alloy phase, forming more active and highly stable sites for methane combustion. Altogether, this work unambiguously clarifies the activity and stability attributes of Pt/Pd phases which often coexist in traditionally synthesized bimetallic catalysts and demonstrates how well-controlled bimetallic catalysts elucidate structure–property relationships.« less

Authors:
 [1]; ORCiD logo [2];  [1];  [1];  [3]; ORCiD logo [4];  [4]; ORCiD logo [1];  [2]; ORCiD logo [5]; ORCiD logo [1]
  1. Stanford Univ., CA (United States). Dept. of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis
  2. Univ. of California, Irvine, CA (United States). Dept. of Chemical Engineering and Materials Science
  3. Stanford Univ., CA (United States). Dept. of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource
  5. Univ. of California, Irvine, CA (United States). Dept. of Chemical Engineering and Materials Science, Dept. of Physics and Astronomy
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:
1390324
Grant/Contract Number:
AC02-76SF00515; DGE-1656518
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 7; Journal Issue: 7; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; hydrothermal stability; methane combustion; monodisperse nanocrystals; Pt/Pd bimetallic catalysts; steam resistance; structure-property relationships

Citation Formats

Goodman, Emmett D., Dai, Sheng, Yang, An-Chih, Wrasman, Cody J., Gallo, Alessandro, Bare, Simon R., Hoffman, Adam S., Jaramillo, Thomas F., Graham, George W., Pan, Xiaoqing, and Cargnello, Matteo. Uniform Pt/Pd Bimetallic Nanocrystals Demonstrate Platinum Effect on Palladium Methane Combustion Activity and Stability. United States: N. p., 2017. Web. doi:10.1021/acscatal.7b00393.
Goodman, Emmett D., Dai, Sheng, Yang, An-Chih, Wrasman, Cody J., Gallo, Alessandro, Bare, Simon R., Hoffman, Adam S., Jaramillo, Thomas F., Graham, George W., Pan, Xiaoqing, & Cargnello, Matteo. Uniform Pt/Pd Bimetallic Nanocrystals Demonstrate Platinum Effect on Palladium Methane Combustion Activity and Stability. United States. doi:10.1021/acscatal.7b00393.
Goodman, Emmett D., Dai, Sheng, Yang, An-Chih, Wrasman, Cody J., Gallo, Alessandro, Bare, Simon R., Hoffman, Adam S., Jaramillo, Thomas F., Graham, George W., Pan, Xiaoqing, and Cargnello, Matteo. Thu . "Uniform Pt/Pd Bimetallic Nanocrystals Demonstrate Platinum Effect on Palladium Methane Combustion Activity and Stability". United States. doi:10.1021/acscatal.7b00393. https://www.osti.gov/servlets/purl/1390324.
@article{osti_1390324,
title = {Uniform Pt/Pd Bimetallic Nanocrystals Demonstrate Platinum Effect on Palladium Methane Combustion Activity and Stability},
author = {Goodman, Emmett D. and Dai, Sheng and Yang, An-Chih and Wrasman, Cody J. and Gallo, Alessandro and Bare, Simon R. and Hoffman, Adam S. and Jaramillo, Thomas F. and Graham, George W. and Pan, Xiaoqing and Cargnello, Matteo},
abstractNote = {Bimetallic catalytic materials are in widespread use for numerous reactions, as the properties of a monometallic catalyst are often improved upon addition of a second metal. In studies with bimetallic catalysts, it remains challenging to establish clear structure–property relationships using traditional impregnation techniques, due to the presence of multiple coexisting active phases of different sizes, shapes, and compositions. Here, a convenient approach to prepare small and uniform Pt/Pd bimetallic nanocrystals with tailorable composition is demonstrated, despite the metals being immiscible in the bulk. By depositing this set of controlled nanocrystals onto a high-surface-area alumina support, we systematically investigate the effect of adding platinum to palladium catalysts for methane combustion. At low temperatures and in the absence of steam, all bimetallic catalysts show activity nearly identical with that of Pt/Al2O3, with much lower rates in comparison to that of the Pd/Al2O3 sample. BUt, unlike Pd/Al2O3, which experiences severe low-temperature steam poisoning, all Pt/Pd bimetallic catalysts maintain combustion activity on exposure to excess steam. These features are due to the influence of Pt on the Pd oxidation state, which prevents the formation of a bulk-type PdO phase. Despite lower initial combustion rates, hydrothermal aging of the Pd-rich bimetallic catalyst induces segregation of a PdO phase in close contact to a Pd/Pt alloy phase, forming more active and highly stable sites for methane combustion. Altogether, this work unambiguously clarifies the activity and stability attributes of Pt/Pd phases which often coexist in traditionally synthesized bimetallic catalysts and demonstrates how well-controlled bimetallic catalysts elucidate structure–property relationships.},
doi = {10.1021/acscatal.7b00393},
journal = {ACS Catalysis},
number = 7,
volume = 7,
place = {United States},
year = {Thu May 18 00:00:00 EDT 2017},
month = {Thu May 18 00:00:00 EDT 2017}
}

Journal Article:
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Cited by: 7works
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  • The quantitative and regioselective synthesis of the mixed-metal cluster (PdPtCo/sub 2/(CO)/sub 7/(dppm)/sub 2/) (1b) was achieved by the reaction of the bimetallic complex (PdPtCl/sub 2/(dppm)/sub 2/) (dppm = /mu/-Ph/sub 2/PCH/sub 2/PPh/sub 2/) with (Co(CO)/sub 4/)/sup /minus//. As a result of phosphorus migration from palladium to cobalt, formal insertion of the Co(CO)/sub 3/ fragment into a metal-phosphorus bond of the precursor exclusively occurs into the more labile P /yields/ Pd bond. The lability of the exocyclic Co(CO)/sub 4/ fragment was evidenced and compared between 1b and (Pd/sub 2/Co/sub 2/(CO)/sub 7/(dppm)/sub 2/) (1a). Although a Pd-Co bond is involved, this lability ismore » very sensitive to the neighboring metal center (Pd or Pt). Transmission of electronic effects from one metal-center to another was evidenced, and a platinum effect was observed in dissociating solvents, where 1a is partly dissociated but 1b is completely dissociated into (PdPtCo(CO)/sub 3/(S)(dppm)/sub 2/)(CO(CO)/sub 4/) (S = solvent). This is a reversible process, as is the equilibrium between 1 and halide anions. Solvento clusters were prepared that possess a labile coordination site on Pd leading to completely regioselective reactions with donor molecules, e.g., phosphines, CO, or C/sub 2/Ph/sub 2/. These ligands are labile (PR/sub 3/ < CO < C/sub 2/Ph/sub 2/ < MeCN < THF), and reversible CO uptake and substitution experiments showed that the Pd-bound CO in 4b is less labile than in 4a, indicating again a platinum effect on the reactive Pd center. The tris(bis(diphenylphosphino)methane) cationic cluster (Pd/sub 2/Co(CO)/sub 2/(dppm)/sub 3/)/sup +/ was isolated, in which all the metal-metal bonds are bridged by dppm ligands. Spectroscopic IR and /sup 1/H, /sup 31/P(/sup 1/H), and /sup 195/Pt(/sup 1/H) NMR data are discussed and confirm that in these reactions the PdMCo(dppm)/sub 2/ (M = Pd, Pt) framework is maintained.« less
  • The recent availability of tetrahedral palladium (PdTH) nanocrystals with cleaned surfaces allowed us to evaluate their facet-specific electrochemical properties as a new support of platinum monolayer (PtML) catalysts. The Pd–PtML core-shell electrocatalyst was examined by combining structural analyses and Density Functional Theory (DFT) with electrochemical techniques. The surfaces of the PdTH core are composed of (111) facets wherein the Pd atoms are highly coordinated and have low surface energy. Our results revealed that in comparison with sphere Pd (PdSP)-supported PtML or pure Pt, the PdTH-supported PtML features more surface contraction and a downshift of d-band relative to the Fermi level.more » These geometric- and electronic-effects determine the higher activity of PtML/PdTH/C for the oxygen reduction reaction (ORR) compared to that of PtML/PdSP/C. This shape-property interdependence illuminated new approaches to basic- and applied- research on Pt-based ORR electrocatalysts of significant importance to the widespread use of fuel cells.« less
  • A Pd{sub 25}Zr{sub 75} glassy metal alloy has been activated by controlled oxidation in air, resulting in highly active catalysts for the catalytic, combustion of methane. The fully oxidized alloy was reduced in hydrogen at different temperatures prior to catalytic investigations resulting in a catalyst containing metallic palladium and zirconia. The reduced materials showed marked differences in BET surface area and specific surface area of palladium, both decreasing with increasing reduction temperature. The loss of surface area was accompanied by an increase of the palladium crystallite size as evidenced by XRD line broadening measurements. Catalysts reduced at low temperatures weremore » faster reoxidized than catalysts reduced at high temperatures. Changes in the chemical behavior of palladium oxide were indicated by different decomposition behavior and reducibility with hydrogen and methane. Kinetic measurements revealed profound differences in catalytic activity for catalysts in dependence of the reduction temperature. Strong correlations between the catalytic activity and the crystallite size as well as the reducibility of palladium oxide with methane were found for catalysts reduced at different temperatures. The correlation between the reduction with methane and the catalytic performance is explained by a redox mechanism involving palladium oxide. The influence of the particle size on the catalytic activity is attributed to a strong interaction of the Pd-containing phases (Pd, PdO) with zirconia. This (support) effect is suggested to become prominent with decreasing Pd-particle size. 35 refs., 9 figs.« less