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Proc Natl Acad Sci U S A. 2017 Sep 5;114(36):9523-9528. doi: 10.1073/pnas.1706836114. Epub 2017 Aug 21.

Redox properties of birnessite from a defect perspective.

Author information

1
Department of Physics, Temple University, Philadelphia, PA 19122; perdew@temple.edu Haowei.Peng@gmail.com.
2
Department of Chemistry, Temple University, Philadelphia, PA 19122.

Abstract

Birnessite, a layered-structure MnO2, is an earth-abundant functional material with potential for various energy and environmental applications, such as water oxidation. An important feature of birnessite is the existence of Mn(III) within the MnO2 layers, accompanied by interlayer charge-neutralizing cations. Using first-principles calculations, we reveal the nature of Mn(III) in birnessite with the concept of the small polaron, a special kind of point defect. Further taking into account the effect of the spatial distribution of Mn(III), we propose a theoretical model to explain the structure-performance dependence of birnessite as an oxygen evolution catalyst. We find an internal potential step which leads to the easy switching of the oxidation state between Mn(III) and Mn(IV) that is critical for enhancing the catalytic activity of birnessite. Finally, we conduct a series of comparative experiments which support our model.

KEYWORDS:

birnessite MnO2; catalysis; small polaron; water oxidation

PMID:
28827355
PMCID:
PMC5594676
DOI:
10.1073/pnas.1706836114
[Indexed for MEDLINE]
Free PMC Article

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