A Novel Method to Indirectly Measure Electro-osmotic Drag and Back Diffusion From Total Water Flow Experiments in PEM...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Proton exchange membranes (PEMs) are crucial in fuel cells.
• Accurate quantification of water transport mechanisms (electro-osmotic drag, back diffusion) is essential for PEM performance.
• Previous methods for calculating transport coefficients had limitations, potentially misattributing water flow drivers.

Purpose of the Study:

• To precisely quantify the electro-osmotic drag and back diffusion components of total water flow across a proton exchange membrane.
• To address the deficiencies in prior research regarding the calculation of individual transport coefficients.
• To develop a more accurate model for predicting water flow in PEMs.

Main Methods:

• Utilized a higher-order polynomial data fit for total water flow to account for hydration state dependency.
• Proposed a methodology combining a theoretical model with experimental data sets.
• Determined component coefficients at each data point by fitting experimental data to the theoretical model.

Main Results:

• Identified that previously assumed negligible fluid drivers significantly impact water flow.
• Demonstrated that linear trendlines and origin forcing in prior research led to inaccurate coefficient measurements.
• Showcased the dependency of electro-osmotic drag and back diffusion coefficients on membrane hydration state.

Conclusions:

• The developed methodology provides a more accurate determination of electro-osmotic drag and back diffusion coefficients.
• Improved understanding of water transport enables better prediction of total water flow.
• Enhanced water management in fuel cells can reduce risks of cathode flooding and membrane dry-out, improving overall efficiency and longevity.