The global shift towards more sustainable energy and transportation solutions is reshaping our economy. Hydrogen has surfaced as a highly adaptable energy source, capable of serving various purposes such as fuel or a raw material. It is expected to significantly contribute to the clean energy transition by aiding in the decarbonization of various sectors, including transportation, heating, and different energy sources, both for industrial and residential use, and as a feedstock to produce substances like ammonia and methanol. But behind the scenes of this clean energy revolution lies a critical, often overlooked component: water. Not just any water, but ultra-pure, precisely treated water that enables the efficient and reliable operation of hydrogen electrolyzers.

The Foundation: Water Technology in Green Hydrogen Production

Green hydrogen is produced through electrolysis, a process that splits water into hydrogen and oxygen using electricity—ideally from renewable sources. This method is central to the green hydrogen narrative because it offers a pathway to zero-emission fuel. However, the success of this process hinges on the quality of the water used.

Mature electrolyzer technology, such as Alkaline Water Electrolyzers (AWE) or Proton Exchange Membrane (PEM) electrolyzers, are configured in such a way that can be considered closed- loops from the perspective of water. Contaminants coming with the water supply (make-up water) would accumulate in the balance of the electrolyzer stack and increase the potential to damage the electrolyzer parts.

Recognizing the importance of water quality on the performance and longevity of electrolyzers, it is evident that "water for hydrogen" should be treated as a purified water stream with precise standards that necessitate a deliberately designed treatment process. This is similar to how boiler makeup water is not merely an ordinary water source, nor is the water used for semiconductor fabrication simply obtained from the tap.

The net water supply: Multi-technology schemes for Make-Up Water Treatment

Regardless of whether the source water for a specific project comes from a municipal supply, surface water, reclaimed wastewater, or seawater, treatment is essential to meet the specifications required for electrolysis; fortunately, the necessary technologies are available to achieve this. A make-up water treatment system typically consists of a combination of technologies in three main categories - pre-treatment to remove solids, colloids, and organic matter; a demineralization stage to remove bulk dissolved solids; and a polishing step to remove the residuals to a minimum level. In terms of technology, combinations of ultrafiltration (UF), reverse osmosis (RO) followed by electro deionization (EDI), could achieve the required quality in most of the scenarios. A highly recommendable practice is to cap the multi-tech system with a mixed bed resin polisher after the EDI. This final step adds a layer of safety to help to ensure minimum residuals can enter into the electrolyzer closed loop.

Beyond Purity: Why PEM Electrolyzers Need Application-Specific Mixed Bed Ion Exchange Resins

Proton Exchange Membrane (PEM) systems operate in a closed-loop configuration, recirculating large volumes of water. However, this loop is vulnerable to contamination from multiple sources: make-up water, leaching from system components, and even the electrolyzer membranes and parts themselves. Over time, impurities like fluoride, silica, and CO₂ can accumulate, leading to corrosion, membrane fouling, and reduced efficiency. These challenges lead to specific additional polishing requirements for the PEM electrolyzers. To combat these challenges and achieve and maintain the accurate water quality needs, experts advocate for the use of application-specific mixed bed ion exchange resins in the so-called Refinement Loop Polishing: Within the PEM system, a side-stream polisher continuously removes contaminants from the recirculating water. Given the high temperatures (60–70°C) and presence of oxidants, this environment demands ion exchange resins (IEX) that are thermally stable and chemically resistant. As an alternative to ion exchange resins, various forms of Electrodeionization (EDI) are considered as a polishing technique in refinement loop.

Why Resins Outperform EDI in the Refinement Loop

While EDI is a powerful technology for producing high-purity water, for example in the make-up water treatment system, it faces limitations in the harsh conditions of the PEM loop. Due to thermal environment (often exceeding 60ºC) combined with an aggressive oxidative environment, the durability of the EDI’s capital components is compromised, even in the so-called temperature resistant EDI, causing the expected durability advantage of EDI vs ion exchange mixed beds lost, and in consequence requiring the replacement of a capital-intensive component.

Traditionally, the ion exchange resin bed is housed in a fixed vessel. In well-engineered setups, the resin can be replaced easily and efficiently after a useful lifespan, helping to ensure consistent water quality without unexpected events.

The Value of High-Temperature-Resistant Resins to support equipment efficiency.

Electrolysis generates excess heat, requiring cooling. If the polishing system needs additional cooling, it adds complexity, cost, and energy consumption. As the industry aims to reduce hydrogen production costs, one strategy is operating electrolyzers at higher temperatures. This means the entire loop, including the polisher, must tolerate higher heat. Technologies that can withstand these conditions will support efficiency improvements. Currently, single-use mixed bed ion exchange with application-specific resins is the leading polishing solution.

Application-specific resins, such as DuPont™ AmberLite™ P2X110, are engineered to thrive in these conditions.

They offer:

• Extended service life, reducing maintenance frequency.
• High removal capacity for a broad spectrum of contaminants
• Elevated temperature tolerance (up to 70ºC in long term operation)
• Low TOC leachables, minimizing the risk of secondary contamination.
• Chemical-free operation, simplifying system design and safety.

These resins are not just a component—they are a strategic enabler of electrolyzer performance and longevity.

Without Water, there is No Green Hydrogen

As green hydrogen scales up, the importance of water treatment will only grow. Poor water quality can compromise electrolyzer performance, inflate hydrogen production costs, and undermine the environmental benefits of the entire process. Conversely, investing in advanced water treatment—especially application-specific ion exchange resins—can protect critical equipment, enhance efficiency, and ensure the long-term viability of green hydrogen projects.

“There is no green without blue.” Water is not just a feedstock in hydrogen production—it’s a strategic asset that must be managed with the same rigor and innovation as any other part of the energy system.