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Title: Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles

Abstract

Doping with a transition metal was recently shown to greatly boost the activity and durability of PtNi/C octahedral nanoparticles (NPs) for the oxygen reduction reaction (ORR), but its specific roles remain unclear. By combining electrochemistry, ex situ and in situ spectroscopic techniques, density functional theory calculations, and a newly developed kinetic Monte Carlo model, we showed that Mo atoms are preferentially located on the vertex and edge sites of Mo–PtNi/C in the form of oxides, which are stable within the wide potential window of the electrochemical cycle. These surface Mo oxides stabilize adjacent Pt sites, hereby stabilizing the octahedral shape enriched with (111) facets, and lead to increased concentration of Ni in subsurface layers where they are protected against acid dissolution. Consequently, the favorable Pt 3Ni(111) structure for the ORR is stabilized on the surface of PtNi/C NPs in acid against voltage cycling. Significantly, the unusual potential-dependent oxygen coverage trend on Mo-doped PtNi/C NPs as revealed by the surface-sensitive Δμ analysis suggests that the Mo dopants may also improve the ORR kinetics by modifying the coordination environments of Pt atoms on the surface. Lastly, our studies point out a possible way to stabilize the favorable shape and composition established onmore » conceptual catalytic models in practical nanoscale catalysts.« less

Authors:
ORCiD logo [1];  [2];  [3]; ORCiD logo [1];  [1];  [1];  [4];  [4]; ORCiD logo [2];  [2]; ORCiD logo [2]; ORCiD logo [1];  [3]; ORCiD logo [2]
  1. Northeastern Univ., Boston, MA (United States)
  2. Univ. of California, Los Angeles, CA (United States)
  3. Johns Hopkins Univ., Baltimore, MD (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1436260
Report Number(s):
BNL-203613-2018-JAAM
Journal ID: ISSN 1530-6984
Grant/Contract Number:  
SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 18; Journal Issue: 2; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; acid dissolution; density functional theory; in situ XAS; kinetic Monte Carlo; Mo−PtNi; ORR

Citation Formats

Jia, Qingying, Zhao, Zipeng, Cao, Liang, Li, Jingkun, Ghoshal, Shraboni, Davies, Veronica, Stavitski, Eli, Attenkofer, Klaus, Liu, Zeyan, Li, Mufan, Duan, Xiangfeng, Mukerjee, Sanjeev, Mueller, Tim, and Huang, Yu. Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles. United States: N. p., 2017. Web. doi:10.1021/acs.nanolett.7b04007.
Jia, Qingying, Zhao, Zipeng, Cao, Liang, Li, Jingkun, Ghoshal, Shraboni, Davies, Veronica, Stavitski, Eli, Attenkofer, Klaus, Liu, Zeyan, Li, Mufan, Duan, Xiangfeng, Mukerjee, Sanjeev, Mueller, Tim, & Huang, Yu. Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles. United States. doi:10.1021/acs.nanolett.7b04007.
Jia, Qingying, Zhao, Zipeng, Cao, Liang, Li, Jingkun, Ghoshal, Shraboni, Davies, Veronica, Stavitski, Eli, Attenkofer, Klaus, Liu, Zeyan, Li, Mufan, Duan, Xiangfeng, Mukerjee, Sanjeev, Mueller, Tim, and Huang, Yu. Fri . "Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles". United States. doi:10.1021/acs.nanolett.7b04007. https://www.osti.gov/servlets/purl/1436260.
@article{osti_1436260,
title = {Roles of Mo Surface Dopants in Enhancing the ORR Performance of Octahedral PtNi Nanoparticles},
author = {Jia, Qingying and Zhao, Zipeng and Cao, Liang and Li, Jingkun and Ghoshal, Shraboni and Davies, Veronica and Stavitski, Eli and Attenkofer, Klaus and Liu, Zeyan and Li, Mufan and Duan, Xiangfeng and Mukerjee, Sanjeev and Mueller, Tim and Huang, Yu},
abstractNote = {Doping with a transition metal was recently shown to greatly boost the activity and durability of PtNi/C octahedral nanoparticles (NPs) for the oxygen reduction reaction (ORR), but its specific roles remain unclear. By combining electrochemistry, ex situ and in situ spectroscopic techniques, density functional theory calculations, and a newly developed kinetic Monte Carlo model, we showed that Mo atoms are preferentially located on the vertex and edge sites of Mo–PtNi/C in the form of oxides, which are stable within the wide potential window of the electrochemical cycle. These surface Mo oxides stabilize adjacent Pt sites, hereby stabilizing the octahedral shape enriched with (111) facets, and lead to increased concentration of Ni in subsurface layers where they are protected against acid dissolution. Consequently, the favorable Pt3Ni(111) structure for the ORR is stabilized on the surface of PtNi/C NPs in acid against voltage cycling. Significantly, the unusual potential-dependent oxygen coverage trend on Mo-doped PtNi/C NPs as revealed by the surface-sensitive Δμ analysis suggests that the Mo dopants may also improve the ORR kinetics by modifying the coordination environments of Pt atoms on the surface. Lastly, our studies point out a possible way to stabilize the favorable shape and composition established on conceptual catalytic models in practical nanoscale catalysts.},
doi = {10.1021/acs.nanolett.7b04007},
journal = {Nano Letters},
number = 2,
volume = 18,
place = {United States},
year = {2017},
month = {12}
}

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Figures / Tables:

Figure 1 Figure 1: (A) ORR polarization curves of Mo−PtNi/C, PtNi/C, and Pt/C catalysts recorded at room temperature in an O2-saturated 0.1 M HClO4 aqueous solution with a sweep rate of 20 mV/s and a rotation rate of 1600 rpm. Insert is high resolution transmission electron microscopy image of Mo-PtNi/C. (B) Themore » Mo K-edge XANES spectra collected on Mo foil, MoO3, and Mo−PtNi/C dry electrode ex situ and in an O2-purged 0.1 M HClO4 electrolyte as a function of applied potentials.« less

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