Operando Exploration of CoAl-LDH: Transformations Driving Alkaline Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• Layered double hydroxides (LDHs) are promising electrocatalysts.
• Understanding in-situ transformations is vital for optimizing performance.
• CoAl-LDH is a model system for studying OER mechanisms.

Purpose of the Study:

• To investigate the morphological, compositional, and electronic structure evolution of CoAl-LDH during the oxygen evolution reaction (OER).
• To elucidate the nanoscale mechanisms of electrocatalyst activation and deactivation.
• To demonstrate the utility of operando techniques for tracking dynamic changes in electrocatalysts.

Main Methods:

• Operando near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.
• Electrochemical atomic force microscopy (AFM).
• Density functional theory (DFT) calculations.

Main Results:

• CoAl-LDH fragments into smaller particles due to Al leaching under OER conditions.
• A resting phase with an average Co oxidation state of 2.5+ is formed.
• This resting phase transforms into the active β-CoOOH phase at higher potentials.
• Operando methods reveal nanoscale structural transformations and element dissolution, contrasting with ex-situ analyses suggesting Co3O4 formation.

Conclusions:

• Selective cation leaching, recrystallization, and morphological restructuring are key mechanisms in electrocatalyst activation and durability.
• Operando techniques provide unprecedented insights into the dynamic nanoscale processes governing electrocatalyst function.
• These findings are critical for designing advanced multi-element materials and understanding practical electrocatalyst behavior.