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Nitrogen‐Rich Manganese Oxynitrides with Enhanced Catalytic Activity in the Oxygen Reduction Reaction
Author(s) -
Miura Akira,
RoseroNavarro Carolina,
Masubuchi Yuji,
Higuchi Mikio,
Kikkawa Shinichi,
Tadanaga Kiyoharu
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201601568
Subject(s) - manganese , catalysis , inorganic chemistry , valence (chemistry) , nitrogen , chemistry , antibonding molecular orbital , oxygen , covalent bond , xanes , electron , spectroscopy , physics , organic chemistry , quantum mechanics , atomic orbital , biochemistry
The catalytic activity of manganese oxynitrides in the oxygen reduction reaction (ORR) was investigated in alkaline solutions to clarify the effect of the incorporated nitrogen atoms on the ORR activity. These oxynitrides, with rock‐salt‐like structures with different nitrogen contents, were synthesized by reacting MnO, Mn 2 O 3 , or MnO 2 with molten NaNH 2 at 240–280 °C. The anion contents and the Mn valence states were determined by combustion analysis, powder X‐ray diffraction, and X‐ray absorption near‐edge structure analysis. An increase in the nitrogen content of rock‐salt‐based manganese oxynitrides increases the valence of the manganese ions and reinforces the catalytic activity for the ORR in 1 m KOH solution. Nearly single‐electron occupancy of the antibonding e g states and highly covalent Mn−N bonding thus enhance the ORR activity of nitrogen‐rich manganese oxynitrides.