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Superior Oxygen Exchange Kinetics on Bi2O3-Based Mixed Conducting Composites
Linn Katinka Emhjellen1, Vincent Thoréton1, Wen Xing2
1Department of Chemistry, Centre for Materials Science and Nanotechnology, University of Oslo, FERMiO, Gaustadalléen 21, NO-0349 Oslo, Norway.
ACS Physical Chemistry Au
|March 31, 2025
Summary
This study reveals that (Bi0.8Tm0.2)2O3-δ-(La0.8Sr0.2)0.99MnO3-δ (BTM-LSM) composites significantly enhance oxygen exchange kinetics for sustainable electrochemical technologies. Dissociative adsorption of oxygen is identified as the rate-limiting step at lower temperatures and oxygen partial pressures.
Area of Science:
- Materials Science
- Electrochemistry
- Chemical Engineering
Background:
- Oxygen exchange kinetics are critical for redox reactions in sustainable electrochemical technologies.
- Developing efficient electrode materials is essential for improving device performance.
- Composite materials offer synergistic properties for enhanced catalytic activity.
Purpose of the Study:
- To elucidate the oxygen exchange mechanism in (Bi0.8Tm0.2)2O3-δ (BTM)-(La0.8Sr0.2)0.99MnO3-δ (LSM) composites.
- To identify the rate-limiting steps in the oxygen exchange process.
- To understand the role of the interface in enhancing oxygen exchange kinetics.
Main Methods:
- Isotope exchange pulse response technique was employed to study oxygen exchange kinetics.
- Serial two-step reaction scheme was used to analyze elementary processes.
- Oxygen partial pressure (pO2) and temperature dependencies were investigated.
Main Results:
- BTM-LSM composites exhibit significantly accelerated oxygen adsorption and incorporation compared to parent phases.
- Dissociative adsorption of molecular oxygen is the rate-limiting step under specific conditions (below 900 °C and 0.002-0.05 atm O2, or below 850 °C and 0.21 atm O2).
- An electrocatalytically active interfacial region (1-40 nm) shows oxygen exchange coefficients 2-3 orders of magnitude higher than the bulk.
Conclusions:
- The BTM-LSM composite interface is crucial for enhanced oxygen exchange, driven by cation interdiffusion or electronic structure changes.
- Two potential oxygen exchange pathways were proposed, with molecular oxygen involvement in the rate-determining step.
- Optimized BTM-LSM composites demonstrate potential for high-performance electrochemical sustainable technologies.
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