Revealing the Intrinsic Oxygen Evolution Reaction Activity of Perovskite Oxides across Conductivity Ranges Using Thin...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Efficient electrocatalysts are crucial for water electrolysis, particularly for the oxygen evolution reaction (OER) at the anode.
• Complex oxides are promising OER catalysts, but their varying conductivity complicates the separation of intrinsic activity from transport limitations.
• Developing clear catalyst design rules remains a significant challenge.

Purpose of the Study:

• To systematically decouple electrical transport limitations from intrinsic catalytic properties in perovskite oxides for OER.
• To establish a methodology for evaluating true catalyst performance independent of bulk resistivity and contact resistances.
• To identify structure-activity relationships for designing superior OER electrocatalysts.

Main Methods:

• Utilized an epitaxial thin film model catalyst approach to systematically investigate perovskite oxides (LaNiO₃-δ, La₀.₆₇Sr₀.₃₃MnO₃-δ, La₀.₆Ca₀.₄FeO₃-δ).
• Tuned electron pathways by comparing insulating and conductive substrates (Nb-doped SrTiO₃) to vary effective path length.
• Employed interfacial dipole layers (LaAlO₃) to mitigate contact resistances and isolate intrinsic catalytic properties.

Main Results:

• Observed that catalytic activity scales with resistivity for large electron pathways due to inhomogeneous current distribution.
• Demonstrated that contact resistances on conductive substrates still limit the determination of intrinsic properties.
• Successfully revealed intrinsic OER properties by eliminating interface resistances, showing similar overpotentials for La₀.₆Ca₀.₄FeO₃-δ and LaNiO₃-δ despite a 3-order difference in resistivity.

Conclusions:

• Intrinsic catalytic activity can be masked by electrical transport limitations in complex oxide electrocatalysts.
• Optimizing the electron pathway is as critical as intrinsic material properties for high-performance OER catalysts.
• This work provides a pathway to discover new, highly active OER catalysts by considering both electronic structure and transport phenomena.