Selection of Ion Exchange Membrane for Water Electrolysis

1、Understanding ion exchange membrane An ion exchange membrane (IEM) is a thin barrier that allows ions to be selectively passed from one electrode of an electrochemical device to another, including but not limited to water electrolysis cells and fuel cells. The ion-exchange membrane consists of a three-dimensional polymer matrix functionalized with charged (or ion-exchange) groups. These fixed charge groups completely or partially repel similarly charged ions (isoions) out of the membrane and allow ions with different charges (counterions) to pass through the membrane. In hydroelectrolytic cells and fuel cells, efficient ion transport is important for achieving high performance, reducing overpotential, and ensuring the overall effectiveness of relevant electrochemical processes.

2、Key considerations when choosing a appropriate IEM

According to the type of fixed charge group in the polymer backbone, IEM can be divided into two types: cationic (CEM) and anion (AEM) exchange membrane. The cation exchange membranes contain fixed negatively charged ions that allow the cations to move on the membrane. Conversely, AEM carries positively charged groups that selectively allow the transport of anions. In addition to these two basic classifications, the IEM can also be a proton exchange membrane (PEM), a bipolar membrane, an amphotropic membrane, and a mixed matrix membrane. In water electrolytic cells and fuel cells, PEM and AEM are the most useful. PEM is a special CEM that can transport protons (H + ions).

1. When choosing an ion exchange membrane, the first consideration is the type of fuel cell and water electrolytic tank. The operation of fuel cells and water electrolytic cells involves the transport of ions; the type of ion to be transmitted determines the appropriate type of ion exchange membrane to be used. Polymer electrolyte membrane water electrolytic cell (PEMWE) and fuel cell (PEMFC) operating under acidic conditions are required to transport H + ions. Thus, both PEMFC and PEMWE use the PEM. In contrast, anion exchange membrane fuel cells (AEMFC) and anion exchange membrane water electrolytic cell (AEMWE) operate in alkaline environments. Both AEMFC and AEMWE used the AEM.

Once the type of IEM suitable for the fuel cell and water electrolytic cell has is identified, it is time to go deeper into the specific characteristics that produce target efficiency and performance.

2、The IEM performance and the balance between them

In general, the properties of the IEM are determined by the characteristics of the polymer backbone and the fixed charge that constitutes its structure. In particular, the density, wettability (hydrophobic or hydrophilic) and morphology of the polymer matrix, as well as the type and concentration of charged functional groups, can affect the performance of IEM. The mechanical, chemical and thermal properties of IEM are mainly influenced by the polymer backbone, while the electrochemical properties, conductivity and overselectivity are determined by the concentration of the fixed charge. Click here to learn more about the key IEM features.

High-performance IEM shall have high ionic conductivity, high ion exchange capacity, near-uniform overselectivity, and excellent dimensional, chemical, mechanical, and thermal stability. However, it is not easy to meet all of these requirements. We can't do everything, and in most cases, we have to find the perfect balance between these features.

3. Working conditions

When finding a suitable IEM for your application, you should also consider working conditions, including temperature, pressure, and humidity levels. Working conditions can affect not only IEM performance, but also its stability. Some IEM have the best performance at high temperatures, while others are designed for low temperature applications. Ensure that the selected IEM supports the device usage environment.

4, the cost of membrane materials

Suppose that we have found a perfectly optimized membrane with both good performance and stability. Another factor to be considered is the cost. Usually, high requirements for performance and stability require high material costs. Therefore, balancing performance requirements and budget constraints is critical because the cost of IEM affects the overall cost of fuel cells and water systems.

Choosing the right ion exchange membrane is the key point in the design of efficient and durable hydrolysis cells and fuel cell systems. By carefully considering the above factors and conducting appropriate tests, you can make informed decisions based on the specific application requirements. Please contact us, our application engineers and in-house hydrolysis cell and fuel cell experts will help you select the best product for your application. Let's work together to pave the way for the development of clean and sustainable energy solutions.