Optimized Electronic Configuration to Improve the Surface Absorption and Bulk Conductivity for Enhanced Oxygen
Xiaoning Li1, Yanhua Sun1, Qingmei Wu2
1Institute for Superconducting & Electronic Materials (ISEM), Australia Institute for Innovation Materials, Innovation Campus , University of Wollongong , Squires Way , North Wollongong NSW 2500 , Australia.
Journal of the American Chemical Society
|January 24, 2019
Summary
Altering layered perovskite oxide composition and structure stabilizes intermediate spin cobalt ions, significantly boosting oxygen evolution reaction (OER) electrocatalyst efficiency by 100 times.
Area of Science:
- Materials Science
- Electrochemistry
- Catalysis
Background:
- High-efficiency electrocatalysts are crucial for the oxygen evolution reaction (OER).
- Stabilizing specific electronic configurations, like the intermediate spin (IS) state, is key to enhancing OER performance.
- Layered perovskite oxides offer a tunable platform for investigating composition-structure-property relationships.
Purpose of the Study:
- To investigate how subtle variations in composition and structure of layered perovskite oxides affect electronic configurations.
- To elucidate the role of these modifications in tuning electrocatalyst efficiency for the oxygen evolution reaction (OER).
- To establish a correlation between structural features, electronic states, and OER performance.
Main Methods:
- Synthesized layered perovskite oxides (Bi7Fe3Ti3O21) with varying cobalt doping (0%, 50%, 100%).
- Analyzed crystal structures using X-ray diffraction (XRD) refinement.
- Determined electronic structures via X-ray absorption spectroscopy (XAS) and magnetic susceptibility measurements (Curie-Weiss law).
Main Results:
- Elongation of oxygen octahedra along the c-axis stabilized Co ions in the intermediate spin (IS) (t2g)5(eg)1 state.
- This stabilization dramatically enhanced electronic conductivity and absorption capacity.
- The 100% Co-doped sample showed a 100-fold increase in OER efficiency compared to the 0% Co sample, with significantly improved current density, reduced Tafel slope, and enhanced double-layer capacity.
Conclusions:
- Composition and structure are critical for stabilizing suitable electronic structures, such as IS Co ions, for efficient OER catalysis.
- Optimized electronic structures with moderate absorption and good electronic conductivity are essential for high-performance electrocatalysts.
- This study provides a pathway for designing advanced OER electrocatalysts by controlling composition and crystal structure.
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