Low-Ir-Content Ir_0.10Mn_0.90O₂ Solid Solution for Highly Active Oxygen Evolution in Acid Media

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Iridium (Ir)-based materials are crucial electrocatalysts for oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE).
• High cost and limited activity of current Ir-based catalysts hinder commercialization.
• Optimizing Ir atom utilization efficiency is critical for developing cost-effective OER catalysts.

Purpose of the Study:

• To engineer a rutile-structured solid solution catalyst with minimal Ir content for enhanced OER performance.
• To identify the optimal Ir content through phase boundary analysis in the IrO₂-MnO₂ system.
• To investigate the catalytic activity and stability of the developed Ir-based catalyst in acidic electrolytes.

Main Methods:

• Synthesis of a rutile-structured IrO₂-MnO₂ solid solution with minimal Ir content (Ir_0.10Mn_0.90O₂).
• Electrochemical evaluation of OER performance in acidic electrolytes, including mass activity measurements.
• Long-term stability testing during proton exchange membrane water electrolysis (PEMWE) operations.
• Density functional theory (DFT) calculations to elucidate the catalytic mechanism.

Main Results:

• The Ir_0.10Mn_0.90O₂ catalyst achieved a mass activity of 1135 A g^-1_Ir at 300 mV overpotential, approximately 50 times higher than commercial IrO₂.
• Demonstrated excellent stability, operating at 200 mA cm^-2 for 120 hours in PEMWE.
• DFT calculations revealed that electron-withdrawing effects on Ir sites promote hydroxylation, enhancing OER activity.

Conclusions:

• The developed Ir_0.10Mn_0.90O₂ solid solution catalyst offers superior OER performance and stability compared to commercial IrO₂.
• This material represents a significant advancement in reducing Ir content for cost-effective water electrolysis.
• The findings provide a pathway for designing highly active and stable electrocatalysts for clean energy applications.