Support-free iridium hydroxide for high-efficiency proton-exchange membrane water electrolysis

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Proton-exchange membrane water electrolyzers (PEMWE) require efficient membrane-electrode assemblies (MEAs).
• High cost and scarcity of iridium (Ir) necessitate reduced catalyst loading in PEMWE.
• Developing support-free catalysts is crucial for advancing PEMWE technology.

Purpose of the Study:

• To develop a high-performance, support-free iridium catalyst for PEMWE.
• To investigate a metal-oxide-based molecular self-assembly strategy for catalyst synthesis.
• To evaluate the catalytic activity and durability of the novel Ir catalyst in MEAs and PEMWE.

Main Methods:

• Utilized a metal-oxide-based molecular self-assembly strategy to synthesize support-free Ir catalyst.
• Characterized the catalyst structure, revealing densely isolated single IrO6H8 octahedra forming hierarchically porous Ir hydroxide particles.
• Fabricated MEAs and tested their performance in a PEMWE system.

Main Results:

• Achieved a high turnover frequency of 5.31 s⁻¹ at 1.52 V for the support-free Ir catalyst in an MEA.
• Demonstrated excellent PEMWE performance with a cell voltage < 1.75 V at 4.0 A cm⁻² at a low Ir loading of 0.375 mg cm⁻².
• The self-assembly strategy resulted in μm-sized hierarchically porous Ir hydroxide particles.

Conclusions:

• The developed support-free Ir catalyst shows significant potential for efficient and cost-effective PEMWE.
• The metal-oxide-based molecular self-assembly approach offers a general strategy for creating advanced support-free catalysts.
• This work contributes to the large-scale implementation of sustainable hydrogen production via water electrolysis.