Degradation Study by Start-Up/Shut-Down Cycling of Superhydrophobic Electrosprayed Catalyst Layers Using a Localized...

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Polymer electrolyte membrane fuel cells (PEMFCs) are crucial for clean energy.
• Understanding degradation mechanisms during operational cycling is vital for PEMFC durability.

Purpose of the Study:

• To investigate the degradation of PEMFCs with electrosprayed cathode catalyst layers during cyclic start-up and shut-down events.
• To compare the degradation rates of electrosprayed catalyst layers with conventional gas diffusion electrodes.

Main Methods:

• Utilized a single PEMFC with an array of reference electrodes for localized potential measurements.
• Performed accelerated degradation testing via start-up/shut-down cycling.
• Analyzed performance loss, cathode catalyst activity, internal resistance, carbon corrosion, and platinum aggregation.

Main Results:

• Inhomogeneous performance loss occurred, more severe near the gas outlet and predominantly during start-up.
• Degradation involved loss of cathode catalyst activity and increased internal resistance due to carbon corrosion and Pt aggregation.
• Electrosprayed catalyst layers exhibited lower degradation rates in the initial 100 cycles compared to conventional electrodes.
• The enhanced durability of electrosprayed layers was linked to their hydrophobic microstructure, which slowed carbon support corrosion.

Conclusions:

• The initial improved durability of electrosprayed cathode catalyst layers is attributed to their microstructure-dependent resistance to carbon corrosion.
• Long-term degradation is primarily governed by the platinum-to-carbon (Pt/C) ratio in the cathode catalyst layer.
• Start-up/shut-down cycling significantly impacts PEMFC performance, necessitating strategies to mitigate degradation, particularly carbon corrosion and Pt aggregation.