Microenvironment Engineering as a Design Principle for Suppressing Catalyst Metal Loss

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Platinum electrocatalysts are crucial for fuel cells but suffer from stability issues.
• Degradation mechanisms like dissolution, redeposition, and restructuring are influenced by the catalyst's microenvironment.
• The combined effects of ionomer chemistry and support porosity on platinum mass balance are not fully understood.

Purpose of the Study:

• To differentiate apparent dissolution from actual platinum loss in electrocatalysts.
• To investigate the role of ionomer-platinum contact and support porosity in catalyst degradation.
• To provide insights into improving electrocatalyst durability.

Main Methods:

• Operando Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to monitor platinum species.
• An ion-exchange method quantified platinum retained within the ionomer.
• Model polycrystalline platinum and supported nanoparticles on porous/nonporous carbon supports were studied.

Main Results:

• Direct ionomer-platinum contact increases intrinsic dissolution but also traps dissolved platinum, creating a discrepancy in measured loss.
• Pore confinement within supports alters degradation pathways, favoring local redeposition and reducing net platinum loss.
• The study successfully distinguished between apparent and actual platinum loss.

Conclusions:

• Ionomer accessibility and nanoscale transport within the catalyst microenvironment are critical for managing platinum mass balance.
• Understanding these factors is essential for designing more durable platinum electrocatalysts.
• The findings offer practical strategies for enhancing electrocatalyst longevity.