Mixed ion and electron transport theory and application in solid oxide conductors

Abstract

Mixed ions and electron conductors (MIECs) are an important family of electrocatalysts for electrochemical devices, such as reversible solid oxide cells, rechargeable metal—air batteries, and oxygen transport membranes. Concurrent ionic and electronic transports in these materials play a key role in electrocatalytic activity. An in-depth fundamental understanding of the transport phenomena is critically needed to develop better MIECs. In this brief review, we introduced generic ionic and electronic transport theory based on irreversible thermodynamics and applied it to practical oxide-based materials with oxygen vacancies and electrons/holes as the predominant defects. Two oxide systems, namely CeO₂-based and LaCrO₃-based materials, are selected as case studies to illustrate the utility of the transport theory in predicting oxygen partial pressure distribution across MIECs, electrochemical electronic/ionic leakage currents, and the effects of external load current on the leakage currents.

Keywords

irreversible thermodynamics / diffusivity / charge neutrality / electrochemical potential / electrostatic potential

References

[1] Ebbesen SD, Jensen SH, Hauch A, Mogensen MB. High temperature electrolysis in alkaline cells, solid proton conducting cells, and solid oxide cells. Chem. Rev., 2014, 114(21): 10697.

[2] C.L. Wang, Y.C. Yu, J.J. Niu, Y.X. Liu, D. Bridges, X.Q. Liu, J. Pooran, Y.F. Zhang, and A.M. Hu, Recent progress of metal—air batteries—A mini review, Appl. Sci., 9(2019), No. 14, art. No. 2787.

[3] Jiang QY, Faraji S, Slade DA, Stagg-Williams SM. A review of mixed ionic and electronic conducting ceramic membranes as oxygen sources for high-temperature reactors. Membr. Sci. Technol., 2011, 14, 235.

[4] Heyne L. Geller S. Electrochemistry of mixed ionic-electronic conductors. Solid Electrolytes, 1977, New York, Springer-Verlag Berlin Heidelberg, 169.

[5] Wagner C. Beitrag zur theorie des anlaufvorgangs. Z. Phys. Chem., 1933, 21B(1): 25.

[6] De Groot SR. Thermodynamics of Irreversible Processes, 1951, Amsterdam, North-Holland Publication Company

[7] Rickert H. Electrochemistry of Solids—An Introduction, 1982, New York, Springer-Verlag Berlin Heidelberg, 79.

[8] Maier J. Physical Chemistry of Ionic Materials: Ions and Electrons in Solids, 2004, Chichester, John Wiley & Sons Ltd, 294.

[9] Murch GE. The haven ratio in fast ionic conductors. Soiid State Ionics, 1982, 7(3): 177.

[10] N.S. Choudhury and J.W. Patterson, Performance characteristics of solid electrolytes under steady-state conditions, J. Electrochem. Soc., 118(1971), No. 9, art. No. 1398.

[11] Riess I. Current—voltage relation and charge distribution in mixed ionic electronic solid conductors. J. Phys. Chem. Solids, 1986, 47(2): 129.

[12] Mineshige A, Yasui T, Ohmura N, Kobune M, Fujii S, Inaba M, Ogumi Z. Oxygen chemical potential and mixed conduction in doped ceria under influence of oxygen partial pressure gradient. Solid State Ionics, 2002, 152–153, 493.

[13] Steele BCH. Appraisal of Ce_1−yGd_yO_2−y/2 electrolytes for IT-SOFC operation at 500°C. Solid State Ionics, 2000, 129(1–4): 95.

[14] Dalslet B, Blennow P, Hendriksen PV, Bonanos N, Lybye D, Mogensen M. Assessment of doped ceria as electrolyte. J. Solid State Electrochem., 2006, 10(8): 547.

[15] Yasuda I, Hikita T. Electrical conductivity and defect structure of calcium-doped lanthanum chromites. J. Electrochem. Soc., 1993, 140(6): 1699.

[16] Yasuda I, Hishinuma M. Electrochemical properties of doped lanthanum chromites as interconnectors for solid oxide fuel cells. J. Electrochem. Soc., 1996, 143(5): 1583.