Engineering electrocatalytic activity in nanosized perovskite cobaltite through surface spin-state transition

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalyst activity is intrinsically linked to electronic structure.
• Shao-Horn's principle established a correlation between oxygen evolution reaction (OER) activity and eg orbital occupation in perovskite oxides, guiding catalyst design.

Purpose of the Study:

• To engineer the eg orbital filling of perovskite cobaltite (LaCoO3) for enhanced oxygen evolution reaction (OER) activity.
• To investigate the effect of particle size reduction on the electronic structure and OER performance of LaCoO3.

Main Methods:

• Facile synthesis method to reduce particle size of LaCoO3 to approximately 80 nm.
• Analysis of eg orbital occupation and cobalt ion spin states using surface-sensitive techniques.
• Electrochemical testing to evaluate oxygen evolution reaction (OER) activity.

Main Results:

• Reducing particle size increased the eg filling of cobalt ions in LaCoO3 from unity towards the optimal configuration of 1.2.
• The engineered LaCoO3 nanoparticles exhibited significantly enhanced OER activity, comparable to state-of-the-art cobalt oxides.
• Emergence of a spin-state transition (low-spin to high-spin) in surface cobalt ions was observed, correlating with enhanced reactivity.

Conclusions:

• Particle size engineering is an effective strategy to tune the electronic structure of perovskite cobaltites for improved OER catalysis.
• The enhanced activity is attributed to optimized eg orbital filling and the surface spin-state transition, creating more reactive sites.
• This work provides a pathway for designing highly active and stable electrocatalysts for water oxidation.