Research output: Contribution to journal › Article › peer-review
Nonstoichiometric oxides as a continuous homologous series : Linear free-energy relationship in oxygen exchange. / Chizhik, Stanislav A.; Nemudry, Alexander P.
In: Physical Chemistry Chemical Physics, Vol. 20, No. 27, 21.07.2018, p. 18447-18454.Research output: Contribution to journal › Article › peer-review
}
TY - JOUR
T1 - Nonstoichiometric oxides as a continuous homologous series
T2 - Linear free-energy relationship in oxygen exchange
AU - Chizhik, Stanislav A.
AU - Nemudry, Alexander P.
PY - 2018/7/21
Y1 - 2018/7/21
N2 - A novel methodology for the analysis of oxygen exchange in practically important nonstoichiometric oxides with mixed ionic electronic conductivity (MIEC) is suggested. It is based on the fact that the kinetic and thermodynamic properties of such oxides vary continuously with oxygen stoichiometry. This allows MIEC oxides to be considered as a homologous series, with the difference that traditional series are discrete in their chemical composition whereas MIEC oxides are continuous in oxygen stoichiometry. Analysis of the relations between Gibbs energies of reactions and activation barriers traditionally performed for homologous series can be useful in studies of oxygen exchange in MIEC oxides. To demonstrate the approach, thermodynamic and oxygen-exchange kinetics parameters are measured as functions of oxygen nonstoichiometry δ for two perovskites, SrCo0.8Fe0.2O3-δ and SrFeO3-δ, having metal-like and p-type semiconducting conductivities, respectively. Both oxides are shown to obey linear free energy relationships of the Brønsted-Evans-Polanyi form in spite of their different types of electronic structures. The results open up new possibilities for understanding the mechanism of the rate determining step of oxygen exchange in MIEC oxides.
AB - A novel methodology for the analysis of oxygen exchange in practically important nonstoichiometric oxides with mixed ionic electronic conductivity (MIEC) is suggested. It is based on the fact that the kinetic and thermodynamic properties of such oxides vary continuously with oxygen stoichiometry. This allows MIEC oxides to be considered as a homologous series, with the difference that traditional series are discrete in their chemical composition whereas MIEC oxides are continuous in oxygen stoichiometry. Analysis of the relations between Gibbs energies of reactions and activation barriers traditionally performed for homologous series can be useful in studies of oxygen exchange in MIEC oxides. To demonstrate the approach, thermodynamic and oxygen-exchange kinetics parameters are measured as functions of oxygen nonstoichiometry δ for two perovskites, SrCo0.8Fe0.2O3-δ and SrFeO3-δ, having metal-like and p-type semiconducting conductivities, respectively. Both oxides are shown to obey linear free energy relationships of the Brønsted-Evans-Polanyi form in spite of their different types of electronic structures. The results open up new possibilities for understanding the mechanism of the rate determining step of oxygen exchange in MIEC oxides.
KW - SURFACE EXCHANGE
KW - ELECTRICAL-CONDUCTIVITY
KW - GAS-PHASE
KW - KINETICS
KW - PEROVSKITE
KW - RELAXATION
KW - DIFFUSION
KW - TRANSPORT
KW - CATIONS
KW - SRCO0.8FE0.2O3-DELTA
UR - http://www.scopus.com/inward/record.url?scp=85050451569&partnerID=8YFLogxK
U2 - 10.1039/c8cp02924e
DO - 10.1039/c8cp02924e
M3 - Article
C2 - 29947385
AN - SCOPUS:85050451569
VL - 20
SP - 18447
EP - 18454
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 27
ER -
ID: 15963092