Hydrogen

An Innovative Generation of Renewable Hydrogen Electrolyzer

10 Oct 2025

X-SEED, a mid-term stage

Eighteen months after its launch, the European project X-SEED is reaching its mid-term stage with promising progress towards developing a new electrolyzer capable of producing renewable hydrogen more efficiently and at lower cost than existing technologies.
Coordinated by Leitat, and with the support of the Clean Hydrogen Partnership under the European Union’s Horizon Europe programme, the project continues to strengthen its position as a potential game-changer to produce cost-efficient renewable hydrogen to drive the decarbonisation of industry and mobility.

Since its official kick-off in January 2024, the X-SEED consortium – composed of Leitat, Snam S.p.A., Particular Materials, Industrie De Nora, and the Technical University of Denmark – has worked intensively to design, model and prepare cell and the key components of the electrolyzer technology that operates with supercritical water. This innovative approach is intended to overcome many of the limitations of current commercial devices, while paving the way for a new generation of hydrogen production systems that are simpler, more efficient and more sustainable.

Project Workshop 2025

Project steps: inception and evolution

preparing the test area, where the cell and stack will be tested using a The first half of the project has focused on designing and validating the fundamental building blocks of the new electrolyzer. Significant progress has been made in three main areas. Firstly, the researchers developed a supercritical membrane-less cell and its stack configuration through electrolyzer design and simulation.

X-SEED has developed both two-dimensional and three-dimensional models to understand better how the electrolyzer operates with water at supercritical conditions and to evaluate its performance. For example, these models have enabled us to determine the most suitable range of feed flow rates, aiming to achieve proper gas separation while staying within any flammability limits. It is worth emphasizing that we are currently working on optimizing these parameters to meet all project requirements, encompassing safety and budget considerations.

Secondly, the development of catalysts and electrodes has led to the creation of more than ten new catalysts using advanced techniques, including electrospinning and continuous hydrothermal flow synthesis. These catalysts were integrated into specially designed electrodes built on durable Inconel mesh. Laboratory tests confirmed that the materials met the project’s technical goals in terms of composition, while their stability, under water at supercritical conditions, is still to be proven. The materials also showed promising electrochemical performance.

Although efficiency and activity targets have not yet been fully reached, the scientists stress that the work is ongoing and further improvements are expected. The team additionally evaluated the sustainability and circularity of the catalysts. In a notable example, they successfully produced nickel oxide (NiO) catalysts using wastewater from the galvanic industry—demonstrating the project’s commitment to greener, more sustainable innovation. And thirdly, the team has begun the test area preparation, where the cell and stack will be tested a custom-built test system designed to operate under supercritical conditions. This setup will enable researchers to conduct in-depth evaluations of a membrane-less process for splitting water at high temperatures and pressures. This approach could open up new pathways for producing renewable hydrogen.

Feasability of a concept

According to Pau Bosch, Scientific Coordinator of X-SEED at Leitat, the progress achieved so far demonstrates the feasibility of the concept and confirms that the consortium is on the right track to deliver a breakthrough technology for renewable hydrogen.

Pau Bosh: Scientific Coordinator of X-SEED at Leitat

Our team has developed more than ten new catalysts that make it possible to produce high-performance electrodes while keeping the content of critical raw materials exceptionally low, below 0.3 mg per watt. While these catalysts are designed for the X-SEED electrolyzer, they could also be adapted for other types of water electrolyzers, opening doors to wider applications. In parallel, we designed a membrane-less supercritical electrolyzer using advanced 2D and 3D simulations. This work allowed us to pinpoint most energy-efficient conditions to produce renewable hydrogen and guarantee the proper and safety separation of gases, paving the way for a new generation of high-performance electrolyzers. Finally, we created a unique reactor capable of measuring electrolyte conductivity across a wide range of temperatures and pressures, including supercritical conditions. Until now, data on the conductivity and physical properties of electrolytes under such extreme conditions has been scarce. This breakthrough not only fills a significant gap in scientific knowledge but also has major industrial implications, enabling the study of a broader range of electrolytes and process waters across a wide range of temperature and pressures.

A new challange

Early results have already shown that the production of renewable hydrogen with a membrane-less electrolyzer is feasible achieving high quality hydrogen stream out of flammability limits by optimum the operational conditions as water flow rates.

This represents an energy and price cost reduction respect conventional electrolyzer technologies as the membranes is one of the weak components causing performance and lifetime limitations as well as raise the electrolyzer costs, reinforcing the potential of X-SEED to increase hydrogen production efficiency, reduce production costs minimise the use of scarce and expensive raw materials, and extend the lifetime of electrolyzers. These advances could make renewable hydrogen not only technically feasible, but also economically competitive when compared to fossil-based hydrogen production routes, accelerating the energy transition in Europe.

Like any ambitious research and innovation project, X-SEED has also faced its share of challenges as lack of information about the properties of different electrolytes at supercritical conditions which difficult the development of the models to design the electrolyzer. Yet, the consortium has managed to overcome them by combining the complementary expertise of leading companies, academic partners and technology developers. This multidisciplinary collaboration remains a cornerstone of the project’s success.

An eye on the future

Looking ahead, the second half of the project will be constructing the test rig of electrolyzer working with water at supercritical conditions and validating and optimizing its performance. This will include building and testing an electrolyzer feasible to work at supercritical conditions, integrate the catalyst and electrodes developed, assessing its performance, efficiency and durability, and ensuring that the new system can operate reliably over long periods.
The consortium will also carry out a comprehensive environmental, social and economic assessment based on life cycle analysis to ensure that the technology is viable from all sustainability perspectives. At the same time, industrial pathways will be explored in collaboration with end-users, so that the electrolyzer can be integrated into existing processes and infrastructures, especially the industries with manufacturing process that requires high temperatures which are very difficult to electrify them to decarbonize.

X-SEED: new hydrogen scenarios in Europe

As the project moves towards its final stages, the consortium is confident that X-SEED will contribute decisively to the competitiveness of renewable hydrogen in Europe. Its potential applications in energy-intensive industries, mobility, and energy storage could play a major role in reducing CO₂ emissions and making Europe less dependent on fossil fuels.

Pau Bosch, Scientific Coordinator of X-SEED at Leitat, highlights the project’s relevance:

All processes that currently rely on fossil fuels and can be electrified should be electrified, but some sectors are harder to decarbonize efficiently. In these cases, hydrogen offers a crucial solution. Producing renewable hydrogen in a cost-effective way is therefore essential for a sustainable future. The X-SEED electrolyzer uses waste heat from high-temperature industrial processes to generate hydrogen. By tapping into this untapped energy source, it reduces electricity consumption and boosts the competitiveness of renewable hydrogen, bringing us closer to a cleaner, more sustainable industrial landscape.

With one and a half years completed and another one and a half to go, X-SEED is consolidating itself as one of the ambitious initiatives in Europe for renewable hydrogen production. The consortium will continue to advance steadily towards the final demonstration of the technology, with the clear goal of enabling a sustainable, cost-competitive and scalable hydrogen economy.