Environmentally Friendly and Flexible AEM Electrolyzers Emerge

Water electrolysis technologies are integral for green hydrogen production. An electrolyzer has two electrodes that are separated by an electrolyte. Based on the electrodes and electrolytes used, an electrolyzer can be divided into four types: alkaline, proton exchange membrane (PEM), solid oxide, and anion exchange membrane (AEM). 

Drivers for AEM Electrolyzers

Alkaline and PEM electrolyzers are the most mature water electrolysis technologies with large-scale deployment. However, they have inherent limitations, which provides impetus for AEM adoption. While PEMs provide flexibility and fast response times, the high cost of materials that are required to achieve long lifetimes and performance is a barrier to the technology’s growth. To account for the high acidic operational environment of PEMs, noble catalyst materials such as iridium, platinum, and titanium are required. These materials are scarce and expensive because they are rare earth metals. Due to the less corrosive operating environment of AEMs, the electrodes used are comprised of steel or nickel alloys, which are common metals. Additionally, AEMs tolerate lower water purity levels, enabling them to operate on rain and tap water and reducing their operational costs. 

Alkaline electrolyzers’ major drawback is that their slow response to power fluctuations makes integrating them with renewable energy a challenge. Furthermore, alkaline electrolyzers require auxiliary purification and compression equipment to produce high pressure, high quality gas, which makes them cumbersome and monolithic. Even though AEM electrolyzers use similar cost-effective materials as alkaline electrolyzers, they do not require any auxiliary equipment to produce purer hydrogen with higher efficiencies. AEMs also possess a flexible modular structure and can be readily powered by renewable energy.

Limitations of AEM Electrolyzers

However, AEM electrolyzers have certain limiting factors that are hindering their growth. First, AEMs exhibit low conductivity, which makes their performance subpar compared with PEMs. To account for this, developers can construct electrolyzers with thinner membranes, but this method compromises structural integrity. Second, AEMs have chemical and mechanical stability concerns that result in unstable lifetime profiles. Lastly, AEMs degrade at high temperatures, which can cause their membranes to convert to form carbonate and emit carbon dioxide.     

Anion Exchange Membrane

(Source: International Renewable Energy Agency)

The Future of AEM Electrolyzers

To address these limitations, R&D projects are targeting improving AEM electrolyzer performance. In Europe, projects such as ANIONE, CHANNEL, and NEWELY are focused on increasing the techno-economic feasibility of these electrolyzers. These projects are expected to enhance the structural stability and operability of these electrolyzers while reducing their capital costs. 

Even though only a few companies have commercialized these electrolyzers, an increasing number of early movers are expected to surface. Enapter and Alchemr, which are on the initial list of AEM electrolyzer vendors, are producing hydrogen for end-use applications in electricity storage, heavy transport, heating, and other industries. 

Once the present shortcomings of AEM electrolyzers are ameliorated, this water electrolysis technology is anticipated to experience significant growth from the mid-2020s onward. This growth will likely be further assisted by the fact that the scale of AEMs is not constrained by the availability of rare earth materials, unlike PEMs.