Understanding the microstructure of a core-shell anode catalyst layer for polymer electrolyte water electrolysis

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Reducing precious metal loading in catalyst layers (CLs) is crucial for lowering costs in polymer electrolyte water electrolysis.
• Developing efficient and durable catalysts is key to widespread adoption of this clean energy technology.

Purpose of the Study:

• To present the first 3D reconstruction of a TiO2-supported IrO2 core-shell CL using X-ray ptychographic tomography.
• To analyze the nanostructure, phase distribution, and connectivity within the catalyst layer.

Main Methods:

• High-resolution X-ray ptychographic tomography at cryogenic temperature (90 K).
• 3D reconstruction of pore space, IrO2, TiO2 support, and ionomer network.
• Analysis of ionic and electronic conductivity.

Main Results:

• IrO2 forms thin, nanoporous shells around TiO2 particles.
• The ionomer exhibits non-uniform thickness and incomplete catalyst coverage.
• TiO2 particles do not form a percolating network, but other phases show high connectivity.
• Ionic conductivity is significantly lower than electronic conductivity in a dry CL.

Conclusions:

• The nanostructure of the catalyst layer, particularly ionomer distribution, influences its performance.
• Support conductivity has a limited impact on the overall CL electrical conductivity.
• Understanding catalyst layer morphology is vital for optimizing water electrolysis efficiency and cost.