What are Anion Exchange Membranes?

Are you curious about what an anion exchange membrane actually is? Before we answer this question fully, it’s important to have an understanding electrolysis and how it relates to fuel cells.  In chemistry, electrolysis uses a direct current to drive what would not otherwise be a spontaneous chemical reaction.  Electrolysis is one of the options available to create hydrogen from renewable resources. With electrolysis this is done by using electricity to split water into atoms of hydrogen and oxygen.

An electrolyzer is made up of an electrolyte, an anode, and a cathode. The latter two are separated by the former material. The type of material used as an electrolyte determines how an electrolyzer will function. Electrolyzers use energy to electrochemically convert water or carbon dioxide to produce syngas or fuels. When renewable energy is used as pictured below, one can produce renewable fuels and chemicals.

A polymer electrolyte membrane, or PEM, electrolyzer has an electrolyte that is composed of a special plastic. How it works is that water reacts at the anode and forms oxygen and hydrogen ions. Those electrons move on to flow through a circuit while hydrogen ions move over the PEM to the cathode. Once at the cathode, the hydrogen ion combines with electrons from the circuit and hydrogen gas is created.

When considering the differences between cation and anion exchange membranes, you need to take a few things into account. Cation exchange membranes (CEM) are based on sulfonic acid and fluorinated polymer groups which serve as the major membrane in proton exchange membrane fuel cells or PEMFC. This is because of their higher levels of durability and conductivity.

Anion exchange membranes, on the other hand, are based on hydrocarbon polymer and quaternary ammonium groups which have in the past had a lower thermal durability and conductivity when placed into a fuel cell. Dioxide Materials in Boca Raton, Florida, has developed Sustainion® membranes that have achieved record performance at 1 A/cm² at 1.9 V with Base Metal Catalysts, delivering the best of alkaline and PEM systems; and the same membranes also offer improved CO2 electrochemical reduction performance and long life in CO2 electrolysis and “CO2 Conversion to Formic Acid and Acrylic Acid. The technology has been validated by three Fortune 500 companies.  Dioxide Materials is offering preproduction samples of Sustainion™ membranes and ionomers for sale to research groups and is in the process of scaling up their technology.

When considering the potential of hydrogen production using electrolysis, there are many opportunities to consider. Electric power generation and hydrogen fuel might be integrated into a wind farm, which would allow the ability to shift production based on need.

That said, it’s important to know that our grid electricity of today is not a great source of electrolysis because the technologies themselves result in greenhouse gases which can cause damage to the environment. One of the possible options is to separate from the grid or mix into the grid as a renewable source of energy.  As intermittent renewable energy sources, such as wind and solar, increase their market penetration, their daily and seasonal variability needs to be balanced out by either peaking power plants or energy storage solutions. While batteries may soon provide short-duration energy storage at reasonable costs, they do not perform as well for multi-day storage. One alternative is power-to-gas (or liquid) technologies, such as water electrolyzers that convert electricity to chemical energy in hydrogen (H2), which can then be stored in pressurized tanks or underground caverns. These systems do allow for longer-term storage at a lower cost but suffer from reduced roundtrip efficiencies.

Fortunately, there is an immediate market need for the renewable fuels that Dioxide Materials will produce. The California Air Resources Board has mandated increasingly strict fuel carbon standards. By 2025, it is unlikely they can be met by any existing technology. There is a similar mandate in for the entire US, through the Energy Independence and Security Act of 2007, although enforcement of the mandate may be changed by the current administration. Dioxide Materials expects to be a leader in providing the technology that is needed to create the low carbon gasoline that California, and the rest of the country needs.

Dioxide Materials is focused on developing green technology to facilitate the production of cost effectiverenewable fuels and chemicals that are environmentally safe. They offer a selection of electrolyzer kits, anion exchange membranes, and more. To find out more about their work or services, please visit www.dioxidematerials.com or email info@dioxidematerials.com.

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