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Correlating Surface Crystal Orientation and Gas Kinetics in Perovskite Oxide Electrodes
Author(s) -
Gao Ran,
Fernandez Abel,
Chakraborty Tanmoy,
Luo Aileen,
Pesquera David,
Das Sujit,
Velarde Gabriel,
Thoréton Vincent,
Kilner John,
Ishihara Tatsumi,
Nemšák Slavomír,
Crumlin Ethan J.,
Ertekin Elif,
Martin Lane W.
Publication year - 2021
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202100977
Subject(s) - materials science , dielectric spectroscopy , oxide , electrode , perovskite (structure) , analytical chemistry (journal) , kinetics , electrochemistry , epitaxy , chemistry , crystallography , nanotechnology , physics , chromatography , quantum mechanics , metallurgy , layer (electronics)
Solid–gas interactions at electrode surfaces determine the efficiency of solid‐oxide fuel cells and electrolyzers. Here, the correlation between surface–gas kinetics and the crystal orientation of perovskite electrodes is studied in the model system La 0.8 Sr 0.2 Co 0.2 Fe 0.8 O 3 . The gas‐exchange kinetics are characterized by synthesizing epitaxial half‐cell geometries where three single‐variant surfaces are produced [i.e., La 0.8 Sr 0.2 Co 0.2 Fe 0.8 O 3 /La 0.9 Sr 0.1 Ga 0.95 Mg 0.05 O 3−δ /SrRuO 3 /SrTiO 3 (001), (110), and (111)]. Electrochemical impedance spectroscopy and electrical conductivity relaxation measurements reveal a strong surface‐orientation dependency of the gas‐exchange kinetics, wherein (111)‐oriented surfaces exhibit an activity >3‐times higher as compared to (001)‐oriented surfaces. Oxygen partial pressure ( p O 2)‐dependent electrochemical impedance spectroscopy studies reveal that while the three surfaces have different gas‐exchange kinetics, the reaction mechanisms and rate‐limiting steps are the same (i.e., charge‐transfer to the diatomic oxygen species). First‐principles calculations suggest that the formation energy of vacancies and adsorption at the various surfaces is different and influenced by the surface polarity. Finally, synchrotron‐based, ambient‐pressure X‐ray spectroscopies reveal distinct electronic changes and surface chemistry among the different surface orientations. Taken together, thin‐film epitaxy provides an efficient approach to control and understand the electrode reactivity ultimately demonstrating that the (111)‐surface exhibits a high density of active surface sites which leads to higher activity.