Proton transport through aqueous Nafion membrane.

Area of Science:

• Materials Science
• Electrochemistry
• Physical Chemistry

Background:

• Proton transport in Nafion membranes is crucial for fuel cell technology.
• Existing models often focus on specific humidity ranges or mechanisms.

Purpose of the Study:

• To develop a comprehensive model for proton transport in Nafion channels across various humidity levels and temperatures.
• To elucidate the interplay of electrostatic, spin, hydrogen bonding, and water screening effects on proton mobility.

Main Methods:

• A novel proton transport model incorporating multiple physical effects.
• Green function method to calculate proton current as a function of temperature.
• Analysis of proton-proton interactions and cluster-to-cluster transfer.

Main Results:

• The model accurately describes proton transport from low to high humidity, bridging surface and Grotthuss mechanisms.
• Proton current increases at low temperatures (<10K) due to spin effects.
• Above 40°C, proton current decreases owing to water loss and polymer contraction.

Conclusions:

• The proposed model offers a unified understanding of proton transport in Nafion membranes.
• Temperature and humidity significantly influence proton conductivity through distinct mechanisms.
• The study provides insights into critical temperature dependence and tunable parameters.