Tuning the Oxygen Reduction Reactivity of Layered Perovskites Using the Jahn-Teller Effect

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Layered perovskite oxides are crucial for electrochemical reactions.
• Understanding local structural distortions is key to optimizing catalyst performance.

Purpose of the Study:

• To investigate how compositional tuning of La1.2Sr0.8Ni1-xCoxO4 affects local structure and oxygen reduction reaction (ORR) pathways.
• To correlate structural distortions with ORR kinetics and product selectivity.

Main Methods:

• Synthesis and structural analysis (crystallography, Raman spectroscopy) of La1.2Sr0.8Ni1-xCoxO4 samples.
• Electrochemical measurements including Tafel slope analysis and rotating ring-disk electrode (RRDE) studies for ORR.
• Analysis of reaction intermediates and products.

Main Results:

• Cobalt incorporation into Ni-rich La1.2Sr0.8Ni1-xCoxO4 causes anisotropic compression of the c-axis and induces localized distortions.
• Structural distortion parameters correlate with Tafel slopes for the ORR, linked to Jahn-Teller effects of Ni(III).
• Cobalt alters apparent ORR selectivity from H2O2 to H2O, but RRDE reveals this is due to catalyzed H2O2 disproportionation.

Conclusions:

• Compositional control of local distortions in layered perovskites is a viable strategy for tuning electrocatalytic activity.
• Cobalt incorporation can mitigate detrimental Ni-induced distortions and activate H2O2 disproportionation.
• Findings guide the design of catalysts and reactors for selective electrochemical synthesis of H2O2.