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Title: Homogenous electrocatalytic oxygen reduction rates correlate with reaction overpotential in acidic organic solutions

Improvement of electrocatalysts for the oxygen reduction reaction (ORR) is critical for the advancement of fuel cell technologies. Herein, we report a series of eleven soluble iron porphyrin ORR electrocatalysts that possess turnover frequencies (TOFs) from 3 s-1 to an unprecedented 2.2 x 106 s-1. These TOFs correlate with the ORR overpotential, which can be changed by modulating the ancillary ligand, by varying the reaction conditions or by changing the catalyst’s protonation state. This is the first such correlation for homogeneous ORR electrocatalysis, and it demonstrates that the remarkably fast TOFs are a consequence of the high overpotential. Computational studies indicate that the correlation is analogous to the volcano plot analysis developed for heterogeneous ORR materials. This unique parallel between homo- and heterogeneous ORR electrocatalysts allows a fundamental understanding of intrinsic barriers associated with the ORR, which can aid the design of new catalytic systems that operate at low overpotential. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences. Additional data is given in the Electronic Supporting Information.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [2] ;  [1]
  1. Yale Univ., New Haven, CT (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Univ. of South Florida, Tampa, FL (United States); Boston College, Chestnut Hill, MA (United States)
  4. Univ. of Washington, Seattle, WA (United States); NOVA Chemicals Corp., Calgary, AB (Canada)
  5. Boston College, Chestnut Hill, MA (United States)
Publication Date:
OSTI Identifier:
1330399
Report Number(s):
PNNL-SA-117180
Journal ID: ISSN 2374-7943; KC0307010; TRN: US1701316
Grant/Contract Number:
AC05-76RL01830
Type:
Published Article
Journal Name:
ACS Central Science
Additional Journal Information:
Journal Volume: 2; Journal Issue: 11; Journal ID: ISSN 2374-7943
Publisher:
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY