Dynamically Stable Active Sites from Surface Evolution of Perovskite Materials during the Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Perovskite oxides are crucial oxygen evolution reaction (OER) catalysts in alkaline environments.
• Identifying the precise active sites in these catalysts remains a significant challenge.

Purpose of the Study:

• To elucidate the origin of OER activity and active site dynamics in a La_1-xSr_xCoO₃ (LSCO) perovskite model.
• To investigate the role of surface evolution and electrolyte interactions in catalyst performance.

Main Methods:

• Surface characterization of LSCO perovskite under OER conditions.
• Electrochemical analysis to determine activity and stability.
• In-situ studies to observe dynamic active site formation.

Main Results:

• OER activity originates from a surface cobalt hydr(oxy)oxide (CoOH) layer on LSCO.
• Trace iron species in the electrolyte interact with CoOH to form dynamically stable active sites.
• The CoOH/LSCO system exhibits a 10-fold increase in stability and a 3-fold higher activity-stability factor compared to nanoscale CoOH clusters.

Conclusions:

• Surface evolution, including A-site dissolution and O-vacancy creation, is key to forming the active CoOH layer.
• The interaction between the CoOH layer and trace Fe species is critical for stable and active OER catalysis.
• New design principles for robust perovskite oxide OER catalysts can be derived from these findings.