Applicability of Single-Layer Graphene as a Hydrogen-Blocking Interlayer in Low-Temperature PEMFCs

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Gas crossover is a critical challenge in proton exchange membrane (PEM) based electrochemical systems.
• Single-layer graphene (SLG) shows promise as a barrier layer for small molecules like hydrogen due to its exceptional properties.
• The practical application of SLG as a gas-blocking interlayer in PEMs requires further investigation.

Purpose of the Study:

• To compare two different methods for transferring SLG onto PEMs.
• To evaluate the effectiveness of SLG as a gas-blocking interlayer in low-temperature PEM fuel cells under various conditions.
• To understand the impact of SLG on membrane performance and water transport.

Main Methods:

• Two SLG transfer techniques onto Nafion XL membranes were employed, creating composite membranes.
• Successful transfer was verified using Raman spectroscopy and ex situ hydrogen permeation tests (dry state).
• Composite membrane performance and hydrogen-blocking ability were assessed in a fuel cell setup under operating conditions (80 °C, humidified gases).

Main Results:

• A 50% reduction in hydrogen permeation was observed in dry conditions after SLG incorporation.
• Fuel cell performance was comparable to reference cells when copper etching residues were avoided.
• Hydrogen crossover reduction decreased to 15-19% under humidified fuel cell operating conditions.
• SLG impaired water transport, potentially affecting membrane water management.

Conclusions:

• SLG can be successfully transferred into PEMs, demonstrating effective hydrogen-blocking in dry states.
• The hydrogen-blocking capability of SLG is significantly reduced under humidified PEM fuel cell operating conditions.
• This reduction is attributed to reversible changes upon humidification and irreversible defects formed during operation.