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Title: Improved Oxygen Reduction Reaction Activity of Nanostructured CoS 2 through Electrochemical Tuning

Abstract

Searching for efficient Pt-free oxygen reduction reaction (ORR) electrocatalysts has been actively pursued among the current electrocatalyst research community. The family of transition-metal chalcogenides, especially cobalt disulfide (CoS 2), has been reported as competitive ORR catalysts. In this work, we perform a detailed analysis of the intrinsic activity in terms of onset potentials and selectivity toward hydrogen peroxide of CoS 2 in both acid and alkaline medium. Our detailed characterizations of this system via X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and calculated bulk and surface thermodynamics and ORR mechanism reveal pH-dependent electrochemical evolution of the CoS 2 surfaces. Using XPS results before and after ORR in combination with density functional theory (DFT) calculations for individual surfaces reveals sulfur to oxygen substitution, and partial dissolution occurs in acidic media, while thin cobalt oxide films supported by CoS 2 are formed in alkaline media. The comprehensive DFT calculations of the ORR activities on these systems reveal that sulfur is an unlikely ORR active site, while undercoordinated Co metal site in the CoS 2 is less active than very active undercoordinated Co metal site in the Co oxide film. Using these guiding principles, we then demonstrate that electrochemical lithium (Li) tuningmore » of CoS 2 in organic electrolyte increases its ORR performance in both acid and alkaline medium. Detailed characterizations demonstrate that the grain size of CoS 2 particle is considerably reduced and has a much richer surface oxygen content after electrochemical Li tuning (LiET-CoS 2) as the direct consequence of the Li galvanostatic cycling. The general efficacy of this method toward transition-metal chalcogenides (T-M-X) is further demonstrated by enhanced ORR activities of CoS and Ni 3S 2 in alkaline and neutral medium, respectively. This work opens up an opportunity for probing more advanced T-M-X-based catalysts.« less

Authors:
ORCiD logo [1];  [2];  [3]; ORCiD logo [4];  [4]; ORCiD logo [5];  [2];  [5];  [2]; ORCiD logo [2];  [2];  [6]; ORCiD logo [7]; ORCiD logo [3]
  1. Nanjing Univ. (China); Stanford Univ., CA (United States)
  2. Stanford Univ., CA (United States). SUNCAT Center for Interface Science and Catalysis, Chemical Engineering
  3. Stanford Univ., CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES)
  4. Nanjing Univ. (China)
  5. Stanford Univ., CA (United States)
  6. Stanford Univ., CA (United States). SUNCAT Center for Interface Science and Catalysis, Chemical Engineering; Technical Univ. of Denmark, Lyngby (Denmark)
  7. SLAC National Accelerator Lab., Menlo Park, CA (United States). SUNCAT Center for Interface Science and Catalysis
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC); Toyota Research Institute; National Natural Science Foundation of China (NNSFC); Natural Science Foundation of Jiangsu Province
OSTI Identifier:
1605394
Grant/Contract Number:  
AC02-76SF00515; BK 20170073; 21675080; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Applied Energy Materials
Additional Journal Information:
Journal Volume: 2; Journal Issue: 12; Journal ID: ISSN 2574-0962
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; oxygen reduction reaction; electrochemical lithium tuning; CoS2; theoretical overpotential; transition metal chalcogenides; grain boundaries; Pourbaix diagram

Citation Formats

Zhao, Wei-Wei, Bothra, Pallavi, Lu, Zhiyi, Li, Yanbin, Mei, Li-Ping, Liu, Kai, Zhao, Zhenghang, Chen, Guangxu, Back, Seoin, Siahrostami, Samira, Kulkarni, Ambarish, Nørskov, Jens K., Bajdich, Michal, and Cui, Yi. Improved Oxygen Reduction Reaction Activity of Nanostructured CoS2 through Electrochemical Tuning. United States: N. p., 2019. Web. doi:10.1021/acsaem.9b01527.
Zhao, Wei-Wei, Bothra, Pallavi, Lu, Zhiyi, Li, Yanbin, Mei, Li-Ping, Liu, Kai, Zhao, Zhenghang, Chen, Guangxu, Back, Seoin, Siahrostami, Samira, Kulkarni, Ambarish, Nørskov, Jens K., Bajdich, Michal, & Cui, Yi. Improved Oxygen Reduction Reaction Activity of Nanostructured CoS2 through Electrochemical Tuning. United States. https://doi.org/10.1021/acsaem.9b01527
Zhao, Wei-Wei, Bothra, Pallavi, Lu, Zhiyi, Li, Yanbin, Mei, Li-Ping, Liu, Kai, Zhao, Zhenghang, Chen, Guangxu, Back, Seoin, Siahrostami, Samira, Kulkarni, Ambarish, Nørskov, Jens K., Bajdich, Michal, and Cui, Yi. Thu . "Improved Oxygen Reduction Reaction Activity of Nanostructured CoS2 through Electrochemical Tuning". United States. https://doi.org/10.1021/acsaem.9b01527. https://www.osti.gov/servlets/purl/1605394.
@article{osti_1605394,
title = {Improved Oxygen Reduction Reaction Activity of Nanostructured CoS2 through Electrochemical Tuning},
author = {Zhao, Wei-Wei and Bothra, Pallavi and Lu, Zhiyi and Li, Yanbin and Mei, Li-Ping and Liu, Kai and Zhao, Zhenghang and Chen, Guangxu and Back, Seoin and Siahrostami, Samira and Kulkarni, Ambarish and Nørskov, Jens K. and Bajdich, Michal and Cui, Yi},
abstractNote = {Searching for efficient Pt-free oxygen reduction reaction (ORR) electrocatalysts has been actively pursued among the current electrocatalyst research community. The family of transition-metal chalcogenides, especially cobalt disulfide (CoS2), has been reported as competitive ORR catalysts. In this work, we perform a detailed analysis of the intrinsic activity in terms of onset potentials and selectivity toward hydrogen peroxide of CoS2 in both acid and alkaline medium. Our detailed characterizations of this system via X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and calculated bulk and surface thermodynamics and ORR mechanism reveal pH-dependent electrochemical evolution of the CoS2 surfaces. Using XPS results before and after ORR in combination with density functional theory (DFT) calculations for individual surfaces reveals sulfur to oxygen substitution, and partial dissolution occurs in acidic media, while thin cobalt oxide films supported by CoS2 are formed in alkaline media. The comprehensive DFT calculations of the ORR activities on these systems reveal that sulfur is an unlikely ORR active site, while undercoordinated Co metal site in the CoS2 is less active than very active undercoordinated Co metal site in the Co oxide film. Using these guiding principles, we then demonstrate that electrochemical lithium (Li) tuning of CoS2 in organic electrolyte increases its ORR performance in both acid and alkaline medium. Detailed characterizations demonstrate that the grain size of CoS2 particle is considerably reduced and has a much richer surface oxygen content after electrochemical Li tuning (LiET-CoS2) as the direct consequence of the Li galvanostatic cycling. The general efficacy of this method toward transition-metal chalcogenides (T-M-X) is further demonstrated by enhanced ORR activities of CoS and Ni3S2 in alkaline and neutral medium, respectively. This work opens up an opportunity for probing more advanced T-M-X-based catalysts.},
doi = {10.1021/acsaem.9b01527},
url = {https://www.osti.gov/biblio/1605394}, journal = {ACS Applied Energy Materials},
issn = {2574-0962},
number = 12,
volume = 2,
place = {United States},
year = {2019},
month = {10}
}

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