Identifying the Active Surfaces of Electrochemically Tuned LiCoO₂ for Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Identifying active sites is crucial for designing efficient catalysts.
• Layered lithium cobalt oxide (LCO) is a material of interest for catalytic applications.
• Oxygen evolution reaction (OER) is a critical process in many electrochemical systems.

Purpose of the Study:

• To investigate the active surfaces of LCO for OER.
• To understand the effect of electrochemical delithiation (De-LCO) on LCO's OER activity.
• To correlate theoretical predictions with experimental observations regarding LCO surface activity.

Main Methods:

• Theoretical calculations to predict OER activity on different LCO surfaces.
• Electrochemical delithiation of LCO.
• Experimental characterization of LCO nanosheets and nanoparticles for OER.
• Acid etching of LCO to modify surface properties.

Main Results:

• The stable (0001) surface of LCO shows high OER overpotential, independent of lithium content.
• Edge sites, specifically (112̅0) and (011̅2) surfaces, are predicted to be highly active for OER and sensitive to (de)lithiation.
• Experimental results show negligible OER enhancement for LCO nanosheets (exposing (0001) surface) but significant enhancement for LCO nanoparticles (exposing edge sites).
• Acid etching LCO to create more edge sites improved OER activity, supporting theoretical findings.

Conclusions:

• OER activity on LCO is primarily governed by edge sites, not the basal (0001) surface.
• Electrochemical delithiation enhances OER by increasing the proportion of active Co4+ sites and shifting oxygen 2p states.
• Surface engineering, such as creating more edge sites, is a viable strategy to boost the catalytic performance of LCO for OER.