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Title: Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies

Abstract

Monometallic (δ-MoN, Mo 5N 6, and Mo 2N) and bimetallic molybdenum nitrides (Co 0.6Mo 1.4N 2) were investigated as electrocatalysts for the oxygen reduction reaction (ORR), which is a key half-reaction in hydrogen fuel cells. Monometallic hexagonal molybdenum nitrides are found to exhibit improved activities over rock salt type molybdenum nitride (γ-Mo 2N), suggesting that improvements are due to either the higher molybdenum valence or a more favorable coordination environment in the hexagonal structures. Further enhancements in activity were found for hexagonal bimetallic cobalt molybdenum nitride (Co 0.6Mo 1.4N 2), resulting in a modest onset potential of 0.713 V versus reversible hydrogen electrode (RHE). Co 0.6Mo 1.4N 2 exhibits good stability in acidic environments, and in the potential range lower than 0.5 V versus RHE, the ORR appears to proceed via a four-electron mechanism based on the analysis of rotating disc electrode results. A redetermination of the structures of the binary molybdenum nitrides was carried out using neutron diffraction data, which is far more sensitive to nitrogen site positions than X-ray diffraction data. In conclusion, the revised monometallic hexagonal nitride structures all share many common features with the Co 0.6Mo 1.4N 2 structure, which has alternating layers of cations inmore » octahedral and trigonal prismatic coordination, and are thus not limited to only trigonal prismatic Mo environments (as was originally postulated for δ-MoN).« less

Authors:
 [1];  [2];  [3];  [1]
  1. Stony Brook Univ., Stony Brook, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1330514
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 54; Journal Issue: 5; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Cao, Bingfei, Neuefeind, Joerg C., Adzic, Radoslav R., and Khalifah, Peter G. Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies. United States: N. p., 2015. Web. doi:10.1021/ic5024778.
Cao, Bingfei, Neuefeind, Joerg C., Adzic, Radoslav R., & Khalifah, Peter G. Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies. United States. doi:10.1021/ic5024778.
Cao, Bingfei, Neuefeind, Joerg C., Adzic, Radoslav R., and Khalifah, Peter G. Mon . "Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies". United States. doi:10.1021/ic5024778. https://www.osti.gov/servlets/purl/1330514.
@article{osti_1330514,
title = {Molybdenum nitrides as oxygen reduction reaction catalysts: Structural and electrochemical studies},
author = {Cao, Bingfei and Neuefeind, Joerg C. and Adzic, Radoslav R. and Khalifah, Peter G.},
abstractNote = {Monometallic (δ-MoN, Mo5N6, and Mo2N) and bimetallic molybdenum nitrides (Co0.6Mo1.4N2) were investigated as electrocatalysts for the oxygen reduction reaction (ORR), which is a key half-reaction in hydrogen fuel cells. Monometallic hexagonal molybdenum nitrides are found to exhibit improved activities over rock salt type molybdenum nitride (γ-Mo2N), suggesting that improvements are due to either the higher molybdenum valence or a more favorable coordination environment in the hexagonal structures. Further enhancements in activity were found for hexagonal bimetallic cobalt molybdenum nitride (Co0.6Mo1.4N2), resulting in a modest onset potential of 0.713 V versus reversible hydrogen electrode (RHE). Co0.6Mo1.4N2 exhibits good stability in acidic environments, and in the potential range lower than 0.5 V versus RHE, the ORR appears to proceed via a four-electron mechanism based on the analysis of rotating disc electrode results. A redetermination of the structures of the binary molybdenum nitrides was carried out using neutron diffraction data, which is far more sensitive to nitrogen site positions than X-ray diffraction data. In conclusion, the revised monometallic hexagonal nitride structures all share many common features with the Co0.6Mo1.4N2 structure, which has alternating layers of cations in octahedral and trigonal prismatic coordination, and are thus not limited to only trigonal prismatic Mo environments (as was originally postulated for δ-MoN).},
doi = {10.1021/ic5024778},
journal = {Inorganic Chemistry},
number = 5,
volume = 54,
place = {United States},
year = {2015},
month = {2}
}

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