How to Select and Evaluate Proton Exchange Membranes?

How Does the Proton Exchange Membrane Work?

Proton exchange membranes (PEMs) consist of a polymer matrix with acidic functional groups that can facilitate the transport of protons while blocking the passage of other species such as gases and liquids.

In a fuel cell, hydrogen gas is supplied to the anode where it undergoes electrochemical oxidation to produce protons and electrons. The protons generated at the anode diffuse through the PEM to the cathode, while the electrons flow through an external circuit, generating electrical power. At the cathode, oxygen gas reacts with the protons and electrons to form water, completing the electrochemical reaction.

Applications of PEMs

PEMs are predominantly used in proton exchange membrane fuel cells (PEMFCs), which are efficient and environmentally friendly power sources for various applications. PEMFCs are widely used in transportation, stationary power generation, and portable electronics due to their high-power density, fast start-up time, and low operating temperature.

Moreover, PEMs find widespread applications beyond fuel cells, including electrolyzers, redox flow batteries, and various electrochemical devices.

PEMs from Alfa Chemistry

Selection of PEMs for Specific Applications

When choosing a PEM for a specific application, several factors must be considered to optimize performance and durability. Key considerations include but not limited to proton conductivity, chemical stability, water management capabilities, mechanical strength, and cost-effectiveness. Here are some steps to help you make an informed decision:

• Understand your operating conditions: Consider the temperature, pressure, mass transfer requirements, and chemical compatibility of your application. Some PEMs perform better at higher temperatures or pressures, while others are more stable in harsh chemical environments.
• Define your performance requirements: Determine the level of proton conductivity, methanol crossover rate, mechanical strength, and durability needed for your application. Choose a PEM that meets or exceeds these requirements to ensure optimal performance.
• Evaluate different types of PEMs: There are several types of PEMs available, such as perfluorosulfonic acid, Sulfonated Polyether Ether Ketone (SPEEK), and Polybenzimidazole (PBI). Consider the characteristics of each type and choose the one that best fits your needs.
• Seek expert advice: If you are not sure which PEM to choose, please feel free to consult Alfa Chemistry's expert team for suggestions based on your specific application requirements.

Classification of PEMs based on materials/preparation methods.[1]

Evaluation Methods of PEM Performance

The performance of proton exchange membranes can be evaluated using various characterization techniques to assess key properties such as proton conductivity, water uptake, ion exchange capacity, mechanical strength, and chemical stability. Common methods include:

• Electrochemical impedance spectroscopy to measure proton conductivity;
• Scanning electron microscopy for morphological analysis;
• Differential scanning calorimetry to examine thermal properties;
• Accelerated stress tests to evaluate durability under harsh conditions;
• Titration method for measuring ion exchange capacity;
• MEA test in fuel cell performance test system.

Reference

1. Peighambardoust, S. et al. International journal of hydrogen energy, 2010, 35(17), 9349-9384.