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Structure–Activity Relationship of Iron Oxides for NO Reduction in the Presence of C 3 H 6 , CO, and O 2
Author(s) -
Ueda Kakuya,
Ohyama Junya,
Sawabe Kyoichi,
Satsuma Atsushi
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201902994
Subject(s) - spinel , oxide , metal , inorganic chemistry , chemistry , reactivity (psychology) , adsorption , iron oxide , cyanide , crystallography , materials science , metallurgy , organic chemistry , medicine , alternative medicine , pathology
Spinel‐type NiFe 2 O 4 exhibited the highest NO reduction activity among base‐metal oxides under simulated exhaust of a gasoline‐powered vehicle. The structure–activity relationship of iron oxides has been investigated through both experimental and computational studies. Spinel iron oxide ( γ ‐Fe 2 O 3 ) exhibited a much higher NO reduction activity than that of iron oxide with other structures ( α ‐Fe 2 O 3 and LaFeO 3 ). Operando IR measurements clarified that the spinel structure facilitated the reaction between NO x and adsorbed oxidized hydrocarbon or cyanide species. The high reactivity of the spinel structure was ascribed to the high adsorption energy of NO, as elucidated by DFT calculations. Furthermore, molecular orbital calculations demonstrated that the local coordination structure of the spinel iron oxide induced the involvement of not only σ but also π orbitals during NO adsorption on Fe atoms. This work clarified the origin of the structure‐dependent activity of metal oxides, with a focus on their local coordination structures.