IrO₂/MnO₂ metal oxide-support interaction enables robust acidic water oxidation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Proton exchange membrane water electrolyzers (PEMWE) face challenges in acidic oxygen evolution reaction (OER) due to sluggish kinetics, poor stability, and high iridium loading.
• Supported catalysts improve Ir utilization but struggle with over-oxidation and dissolution.
• Developing efficient and stable catalysts with reduced iridium content is crucial for practical PEMWE applications.

Purpose of the Study:

• To design and synthesize a low-iridium, durable electrocatalyst for acidic OER by leveraging the redox properties of Mn3+/Mn4+ as electronic modulators.
• To enhance the activity and stability of iridium-based catalysts for oxygen evolution reaction (OER).
• To investigate the potential of IrO2/MnO2 as an anode catalyst in proton exchange membrane water electrolyzers (PEMWE) for efficient green hydrogen production.

Main Methods:

• Anchoring IrO2 nanoparticles onto MnO2 nanowires using a molten salt-assisted synthesis method to create the IrO2/MnO2 electrocatalyst.
• Characterizing the catalyst's electronic structure and metal-support interactions.
• Evaluating the electrocatalytic performance and durability in acidic OER and within a PEMWE setup.

Main Results:

• The IrO2/MnO2 catalyst demonstrated a 7-fold increase in intrinsic activity and superior durability compared to commercial IrO2.
• Dynamic electron transfer between Ir and Mn facilitated rapid formation of highly oxidized iridium sites while preventing excessive oxidation.
• A PEMWE with IrO2/MnO2 achieved 2000 mA cm-2 at 1.89 V with low Ir loading (0.5 mg cm-2) and low energy consumption (45.58 kWh kg-1 H2).

Conclusions:

• The developed IrO2/MnO2 electrocatalyst offers enhanced kinetics and stability for acidic OER, addressing key challenges in PEMWE.
• This catalyst enables cost-effective green hydrogen production with a projected cost of $0.9 kg-1 H2, surpassing US-DOE targets.
• The strong metal-support interaction and redox modulation by Mn are key to the catalyst's superior performance and durability.