Unveiling the Local Effects of PTL Passivation in PEM Electrolyzers through Gas and Current Mapping Using Operando...

Area of Science:

• Materials Science
• Electrochemistry
• Physics

Background:

• Anodic titanium (Ti)-based porous transport layers (PTLs) are critical for high-efficiency proton exchange membrane water electrolyzers (PEMWEs).
• PTL/catalyst layer interface passivation is a major challenge in PEMWE development, often mitigated by precious metal coatings like platinum (Pt).

Purpose of the Study:

• To investigate current distribution within PTLs under Ti passivation conditions during PEMWE operation.
• To evaluate the efficacy of Pt coating in preventing Ti passivation using polarized neutron imaging (PNI).

Main Methods:

• Electrochemical studies of PEMWEs with pristine Ti PTLs and Pt-coated PTLs.
• Ex situ electronic and structural characterizations.
• Operando polarized neutron imaging (PNI) for current distribution mapping.
• High-resolution operando neutron radiography.

Main Results:

• Pt coating reduced overpotential by 822 mV at 1 A cm⁻² (1.771 V vs. 2.539 V for pristine Ti PTL).
• Ex situ characterizations could not detect Ti passivation, suggesting a temporary process during operation.
• PNI demonstrated that electrical current preferentially flowed through the Pt-coated PTL.
• Neutron radiography showed approximately 60% of produced oxygen originated from the Pt-coated PTL.

Conclusions:

• Pt coating effectively prevents Ti passivation and enhances PEMWE performance.
• PNI is a valuable tool for understanding current distribution and passivation phenomena in operating PEMWEs.
• The findings highlight the importance of PTL surface modification for efficient water electrolysis.