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Title: Medium Effects are as Important as Catalyst Design for Selectivity in Electrocatalytic Oxygen Reduction by Iron-porphyrin Complexes

Several substituted iron porphyrin com-plexes were evaluated for oxygen reduction reaction (ORR) electrocatalysis in different homogeneous and heterogeneous media. The selectivity for 4-electron re-duction to H2O vs. 2-electron reduction to H2O2 varies substantially from one medium to another for a given catalyst. In many cases, the influence of the medium in which the catalyst is evaluated has a larger effect on the observed selectivity than the factors attributable to chemical modification of the catalyst. For instance, introduction of potential proton relays has variable effects depending on the catalyst medium. Thus, comparisons of ORR selectivity results need to be interpreted with caution, as the catalysis is a property not just of the catalyst, but also of the larger mesoscale environment be-yond the catalyst. Still, in all the direct pairwise comparisons in the same medium, the catalysts with potential proton relays have similar or better selectivity for the preferred 4e– path. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.
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Publication Date:
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Report Number(s):
Journal ID: ISSN 0002-7863; KC0307010
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Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 137; Journal Issue: 13
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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Country of Publication:
United States