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Efficient energy conversion systems need a chemical barrier, a membrane. The polymer membrane acts as an electrolyte, separating hydrogen and oxygen while only permitting the passage of certain ions. Ion-exchange materials can selectively filter positive or negative ions, including acid and base ions. Additionally they interrupt side reactions, increasing the block’s efficiency.
So in the case of a fuel cell, Hydrogen enters at the anode part where it get separated by its electrons. These electrons then travel through the vehicle’s circuit to the cathode in the form of electricity.
There are two main types of exchange membranes depending on the type of ions that they allow through.
Proton exchange membranes are the most popular, industry standard electrolytes. As the name implies, the membrane exclusively allows positively charged atoms to pass through. Their efficiency has been tested and they have been implemented in manufacturing processes but they can be really expensive and less “Green” due to the precious metal catalysts required.
But not all PEM membranes are the same and there’s definitely room for improvement for this kind of fuel cell stack. Pemion, for example, can add to life and efficiency due to the order of magnitude reduction in H2/N2 crossover. It has lower pollution impact and can heavily reduce platinum dissolution while eliminating EOL bioaccumulative toxicity.
Proton exchange membrane (PEM) fuel cells are also referred to as polymer electrolyte membrane fuel cells. This type of fuel cell uses a polymer electrolyte and operates at lower temperatures of around 80 degrees Celsius. PEM fuel cells are more suitable for mobile and back-up power applications due to their high-power density and quick start-stop capabilities.
Proton exchange membranes are great for the time being but they are limited by the required catalysts and the platinized titanium components. That’s why we would expect a pendulum swing towards AEM. What’s AEM? You might ask...
Anion exchange membranes such as AEMION, allow through negatively charged atoms. They make the stack more cost efficient since they reduce the catalyst cost by enabling precious-metal free systems; thus reducing the cost of catalysts, the main cost driver for PEM based fuel cells.They also reduce transport layer costs by eliminating platinised titanium and enabling stainless steel components for simplified and automated machining. Those two simple facts should be enough to make AEM the electrolyte of choice, but the advantages do not stop there.
AEM combine the benefits of both Alkaline and PEM legacy systems. They have very low H2 crossover, high volumetric efficiency and allow rapid cycling for grid balancing.
Anion exchange membranes can also be a great solution to the struggling Hydrogen vehicles
Hydrogen vehicles are currently limited by:
AEM can put an end to this by:
That’s all great and all. But why aren’t they more popular? The main drawback is that they are not implemented in mass production yet so people are still learning about their usage and existence. An industry wide change should be expected in the following years but new technology adoption is always a lengthy procedure.
If you are interested in pioneering in this field with Anion exchange membranes as thin as 15um such as AEMION+™ - AF2-HLE8-15-X or even high conductivity catalyst ink polymers that enable precious metal free systems you can contact us for more information.