Mechanistic Study of IrO₂ Dissolution during the Electrocatalytic Oxygen Evolution Reaction

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Efficient and durable water electrolyzers are critical for sustainable energy technologies.
• Iridium-based materials are leading electrocatalysts for the oxygen evolution reaction (OER) in acidic conditions.
• The degradation mechanisms of these catalysts, particularly iridium dissolution, require deeper understanding.

Purpose of the Study:

• To investigate the mechanistic interplay between activity and stability of iridium-based water splitting electrocatalysts.
• To elucidate the process of iridium dissolution at the IrO2(110)/water interface using first-principles calculations.
• To understand how iridium dissolution intermediates influence OER activity and catalyst degradation.

Main Methods:

• First-principles calculations were employed to simulate iridium dissolution at the IrO2(110)/water interface.
• Thermodynamic stability of surface-bound iridium dissolution intermediates was analyzed across a potential window.
• The OER activity of these intermediates was compared to the pristine IrO2(110) surface.

Main Results:

• Surface-bound IrO2OH species are thermodynamically stable and transform into IrVI (IrO3) at high potentials and IrIII (Ir(OH)3) at low potentials.
• High-valence surface-bound iridium intermediates exhibit enhanced OER activity compared to the pristine IrO2(110) surface.
• These findings align with experimental observations of high activity in amorphous hydrated iridium oxide surface layers.

Conclusions:

• The study illuminates the mechanistic details of iridium oxide degradation during OER.
• Dissolution intermediates play a key role in both catalyst degradation and enhanced OER activity.
• Understanding these coupled processes is vital for designing more stable and efficient iridium-based electrocatalysts for water splitting.