Durable Thin-Film Porous Transport Electrodes for High Current Density PEM Water Electrolysis

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Energy

Background:

• Proton exchange membrane water electrolyzers (PEMWE) require expensive iridium (Ir)-based catalysts for efficient hydrogen production.
• Reducing Ir loading in PEMWE is crucial for lowering system costs while maintaining performance and durability.
• Sputter deposition offers a scalable method for creating uniform, low-loading catalyst layers with controlled composition.

Purpose of the Study:

• To investigate the activity and durability of sputter-deposited metallic Ir, amorphous Ir oxides, and rutile Ir oxides in a porous transport electrode (PTE) architecture.
• To evaluate the potential of low-Ir-loading PTEs for cost-effective hydrogen production in PEMWE.

Main Methods:

• Sputter deposition was used to deposit metallic Ir, amorphous Ir oxides, and rutile Ir oxides onto porous transport layers.
• The activity and durability of these catalyst layers were evaluated in a PEMWE setup at a current density of 3 A cm⁻² with 0.1 mg Ir cm⁻² loading.
• Dissolution rates and voltage decay were measured to assess material stability and long-term performance.

Main Results:

• Metallic and amorphous Ir oxide catalysts exhibited higher initial activity compared to rutile IrO₂.
• Rutile IrO₂ maintained performance beyond 100 hours at 3 A cm⁻² with 0.1 mg Ir cm⁻², showing a 50 mV improvement after 700 hours.
• Rutile IrO₂ demonstrated a >10x reduction in dissolution rate and achieved a steady-state voltage decay rate of 6 µV h⁻¹ with a low-porosity transport layer and 0.4 mg Ir cm⁻² loading.

Conclusions:

• Sputter-deposited rutile IrO₂ in PTEs offers superior durability and stability for low-loading applications in PEMWE.
• The use of rutile IrO₂ PTEs with optimized porosity and loading can significantly reduce hydrogen production costs.
• This approach presents a viable strategy for enhancing the economic feasibility of green hydrogen generation.