The facility in the factory building on the Evonik site in Marl is the size of a double truck-trailer combination. When Production Manager Florian Roghmans explains what goes on here, he has to speak up against the noise of the ventilation system: “This is where the carrier film is drawn into the machine,” explains the chemical engineer, pointing to a transparent roll on the left-hand side of the unit. The web, which is one meter wide and just a few micrometers thick, passes under a container filled with a honey-yellow liquid—the polymer solution. A squeegee gently applies the liquid to the web so that a thin film is visible. Wet with the polymer and stretched taut, the web runs into the center section of the large system, to the dryers. Inside these, nozzles blow warm air against the film until it emerges dried at the other end after a few minutes. “It all looks very simple, but it’s quite sophisticated,” says Roghmans. “The polymer must dry slowly and evenly on the carrier film, otherwise there will be cracks or defects—and that means rejects.”
Before the coated film is rolled up, cameras scan the surface. No scratches, no air bubbles, not even pinhead-sized holes should be visible in the polymer layer. Perfection is required because the component must deliver top performance in its later use—as the heart of an innovative electrolysis technology with which green hydrogen can be produced efficiently and relatively inexpensively.
Proven technologies with weaknesses
Hydrogen, a colorless and odorless gas, is considered to be an environmentally friendly energy source for the future if it is produced using green electricity. The global demand for hydrogen is already around 100 million tons per year. This hydrogen is usually made from natural gas. Using electrolysis is more sustainable. Here, electricity from renewable energy sources is used to split water into its hydrogen and oxygen components. Switching to green hydrogen would thus reduce CO2 emissions by around one billion tons. This corresponds to around one third of the EU’s energy-related emissions.
»If we want to stop using fossil fuels, there’s no getting around hydrogen«
Christian Däschlein Head of New Growth Area AEM at the Evonik Innovation Factory
However, the current electrolysis processes have drawbacks: Depending on the technology involved, the facilities needed for them have to be very large or else equipped with components made from expensive raw materials. The new polymer membrane from Marl, which is known as DURAION®, is now set to pave the way for an electrolysis technology that combines the advantages of established processes and avoids their weaknesses: AEM electrolysis. AEM stands for anion exchange membrane—a layer that separates two electrolysis half-cells in which hydrogen and oxygen are respectively produced. The hydroxide ions (OH-) formed during electrolysis pass through the membrane.
The membrane makes the difference
How electrolysis splits water into hydrogen and oxygen using an anion exchange membrane (AEM)
The chemist Christian Däschlein is certain that hydrogen will play an important role in the transformation of industry toward greater sustainability and resilience. “If we want to stop using fossil fuels in the future in order to reduce CO2 emissions, there’s no getting around this energy carrier,” says Däschlein, who works at the Evonik Innovation Factory. “It’s also essential for making our energy system more resilient and thus making Europe more independent.” Däschlein got the membrane ready for the market with his team of more than 30 people. The chemical and steel industries need hydrogen, and gas-fired power plants will also increasingly be operated using it. “It’s crucial that the electrolyzers are supplied with electricity from renewable sources,” says the Evonik expert. “That’s because only green hydrogen makes sense when it comes to decarbonizing processes and products in these industries over the long term.” Around 100 million tons of hydrogen are currently required worldwide each year. According to estimates, demand is set to rise to between 300 and 700 million tons by 2050, depending on the scenario. Consulting firms predict that 60 to 70 percent of this hydrogen will be green hydrogen.
The new DURAION® membrane could give the hydrogen economy an additional boost. Moreover, with the new pilot plant in Marl, a facility is now available that can meet the growing global demand for membranes for AEM electrolysis.
The advantages offered by AEM electrolysis become apparent when it is compared with conventional processes—AEL (alkaline electrolysis) and PEM electrolysis (proton exchange membrane). What all electrolyzers have in common is the fact that the hydrogen and oxygen are cleanly separated from each other in the two half-cells so that the explosive oxyhydrogen reaction familiar from chemistry lessons does not occur. This requires a separating layer such as the DURAION® membrane.
AEL is the classic method that has been used to produce hydrogen for decades. For technical reasons, however, the electrolyzers used here only work with moderate current densities and do not operate under pressure, as otherwise too much hydrogen would accumulate on the oxygen side. So they must be very large in order to produce economically relevant quantities of hydrogen. In addition, the gas must then be compressed—which requires a great deal of energy—so that it can be stored and transported.
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PEM electrolysis works with higher current densities and under pressure and delivers significantly more hydrogen than an AEL system of the same size. Water is split here under highly acidic conditions. Corrosion-resistant materials must therefore be used—for example precious metals such as iridium. This makes the electrolyzers expensive. The membrane must also be able to withstand the acid. It is usually made of resistant PFAS. However, this group of fluorine compounds has been criticized for years because they accumulate in the environment and are suspected of being potentially harmful to health. This is precisely where DURAION®’s market opportunity lies, as no PFAS are added when the membrane is manufactured. The membrane is therefore an efficient alternative that already offers electrolyzer manufacturers planning security with respect to future environmental regulations.
The best of both worlds
AEM technology avoids the disadvantages of AEL and PEM. It works with higher current densities and under pressure, thus delivering a high hydrogen yield. In addition, the membrane works in an alkaline environment, not in an acidic one. Precious metals are therefore not required for cell design or for use as catalysts; less expensive metals such as nickel can be used instead. The investment costs for AEM technology are thus lower—an important factor for large-scale applications such as those that are being planned in China.
In addition, AEM electrolyzers can be started up more quickly than AEL systems, for example. The technology is therefore very well suited for cushioning the fluctuating supply of solar and wind energy. If there is a lot of electricity available on a sunny and windy day, AEM electrolyzers can ramp up their output at short notice and produce hydrogen. Up until now, the surplus has been diverted to neighboring countries via the European power grid, or power plants have actually been shut down. The resulting compensation and grid congestion costs are borne by the grid operators and ultimately the electricity customers. “We could instead use the surplus electricity to produce hydrogen at virtually zero cost,” says Christian Schnitzer, who is responsible for DURAION® at the High Performance Polymers business line.
Despite these advantages, AEM remains more of a niche technology. Until now, there has been a lack of efficient and reliable membranes that can be produced in large quantities. Various start-ups have launched a number of anion-conducting membranes on the market in recent years. So far, however, no one has been able to supply membranes in the consistent quality and sufficient quantities that would enable a breakthrough for AEM technology. Thanks to its complete backward integration—from the starting molecules to the finished membrane roll—Evonik can meet both requirements with DURAION®. With the plant now in operation, the membrane is available on a large scale. “With our coating width of 100 centimeters, we will be able to supply even the largest AEM electrolyzers with membranes,” says Schnitzer.
A long journey.
Following initial tests, customers praised the overall package of availability, quality, and properties of the membranes, which are chemically and mechanically stable as well as very good anion conductors. They are also gas-tight, which means they can withstand high pressures.
The road to series production of the high-performance membrane was a long one. “The idea came about more than ten years ago, when we made the decision to focus on hydrogen,” says Schnitzer. “Evonik has a lot of expertise with regard to membranes, for example in products for the treatment of gases. So it made sense to also address electrolysis.”
The team began by developing the polymer. It was clear that the material had to fulfill many requirements, and the right building blocks—the monomers—also had to be found. The chemical structure of DURAION® was established around five years ago. “Back then, we were already testing the properties of the developed polymer in membrane form,” says Däschlein. Two years later, the team also developed a version with fabric reinforcement in order to meet all customer requirements. “In the beginning, we manufactured both products by hand as films in approximately A4 format,” Däschlein explains.
The next step was the scale-up—the step from laboratory scale to bulk production—in this case of both the polymer solution and the membranes. There is a huge difference between producing 100 grams of a polymer in a small glass flask in the laboratory and producing hundreds of kilos in a large vessel. The components are quickly mixed in the laboratory flask and the heat is distributed evenly. In a large vessel, uniform mixing and heating become a challenge. “Fortunately, we have the necessary expertise in-house—everything from basic chemistry to plant construction,” says Däschlein. “For the scale-up, we brought together specialists from various locations.”
Growing step by step
However, it still took some time before roll-to-roll production in the 20-meter unit became possible. The team approached the big solution slowly. Initially, the experts produced 13-cm-wide membranes on a laboratory system the size of a living room wall unit. This allowed them to test how well the polymer can be produced in a continuous process in order to perfectly match the machine and material. About three years ago, Roghmans and his team started planning the next expansion stage: “We then had an idea of how the membrane could be produced roll-to-roll, but a large system is something completely different,” he says. “For example, the air flow and heat are distributed very differently than in a small system.”
In addition, it had to be possible to combine the liquid polymer layer with a thin reinforcing fabric. This fabric ensures that the membranes swell less during operations in the electrolyzer and therefore do not wrinkle the way human skin does after a long bath. Ion-conducting polymers absorb water, which means that they expand by 10 to 20 percent in a wet environment. If a water-repellent fabric is embedded in the polymer, it reduces water absorption and prevents the membrane from creating waves in the electrolyzer. “This is primarily an issue with large electrolyzers in which the membranes installed occupy a large area,” Roghmans explains. The plant in Marl therefore had to be able to position the reinforcing fabric precisely in the polymer so that it is embedded exactly in the middle of the wafer-thin honey layer and does not protrude from the top or bottom of the membrane. To do this, the system unwinds the carrier film and the fabric from two rolls at the same time. At the point where the fabric and the coated web meet—the lamination point—it is pressed into the polymer solution.
Large-scale production
The pilot plant began operating recently. “This is no longer a research unit, but instead the actual starting point for bringing our product to market,” says Däschlein. “In the current expansion stage, we are able to produce membranes for an electrolysis capacity of up to 2.5 gigawatts.” This corresponds to a quarter of Germany’s planned electrolysis capacity for the year 2030.
The first manufacturers of AEM electrolyzers are already using DURAION® membranes in pilot production and demonstration plants. “We can now supply not only large quantities but also consistently high quality,” says Däschlein. This is the be-all and end-all for manufacturers of electrolyzers.
The DURAION® membrane, and with it AEM technology, could bring new momentum to hydrogen production. The technology is reliable and robust, reduces investment costs for electrolyzers, and can now be brought to market on a large scale thanks to roll-to-roll mass production. The expansion targets in Germany and Europe have been set high in recent years. For example, in its update of the National Hydrogen Strategy, the German government set a target of 10 gigawatts of electrolysis capacity for 2030—that corresponds to around 12 percent of the installed wind turbine capacity in Germany.
The expansion has stalled, however, and only 7.2 gigawatts are now firmly planned, according to the German Gas and Hydrogen Industry Association. “Numerous electrolysis projects have been postponed or canceled, particularly on the production side, as the funding conditions are inadequate,” says the association’s Managing Director, Timm Kehler. In addition, it is not certain that the hydrogen produced will also be accepted (see the interview with Dr. Ann-Kathrin Klaas).
Germany and Europe are facing a chicken-and-egg problem, according to Kehler: Does the hydrogen have to be there first, or does the demand? “We need practical and reliable conditions for the production of hydrogen—especially green hydrogen,” says Kehler. “This means that the government has to set a binding target for the expansion of electrolysis, arrange long-term purchase agreements, and ensure competitive electricity prices.” Only then would companies have the investment security they need, and only then could the ramp-up be accelerated. The DURAION® membrane could make a significant contribution to this process. After all, it has the potential to make electrolysis more cost-efficient than before. In addition, Evonik is a reliable supplier of AEM technology.
The hydrogen market currently displays a much greater degree of momentum in China. While regulatory barriers are still being debated in Europe, hydrogen is already firmly anchored in the national strategy in China. The dynamics there are not a distant scenario for Evonik, but instead a direct business development: AEM electrolyzers are already widely used in Asia and the demand for high-performance membranes is enormous. “The technology is already being scaled up to industrial proportions there,” Schnitzer reports. Asia is therefore an interesting market for the membranes from Marl.
Schnitzer is optimistic that hydrogen will prevail, sooner or later, initially in Asia and Europe—and its use will expand accordingly: “When this becomes the case, we will be there to produce large quantities of membranes—at an attractive price.”
Marl meets Shanghai
Evonik’s new application technology center starts operations in China
Demand for hydrogen is growing in China—and with it interest in AEM technology. Evonik is positioning itself strategically here. Parallel to the start of membrane production in Germany, the new AEM Center Shanghai has commenced operations in China. This is the company’s first technology-oriented application technology center in Asia with a focus on AEM electrolysis and its integration into the hydrogen infrastructure.
Experts there test the membranes produced in Marl together with local partners and customers under real operating conditions. The center is aimed at global customers and is also closely linked to the Chinese market—with the goal of quickly transferring AEM technology to industrial applications and promoting its dissemination.
