Climate change has significant impacts on the environment, health, and economy. It is imperative to reduce energy consumption, increase efficiency, and decarbonize economy. Increasing energetic efficiency is no longer sufficient - a radical paradigm shift is needed, starting with energetic carriers. Hydrogen (H2) is expected to play a key role: It is essential for ensuring the energy security of the European Union (EU) and becoming the world’s first climate-neutral continent by 2050. The REPowerEU plan aims at producing 10 million tons of green H2 in the EU. Green H2 is obtained mainly by electrolysis (the decomposition of water molecules into oxygen (O2 and H2). There are several types of electrolysers: alkaline (AWEL), proton exchange membrane (PEMEL), solid oxide (SOEL), anion exchange membrane (AEMEL). AWEL and PEMEL are already commercial but have three main bottlenecks: high production costs (5-8 €/kg H2), limited efficiencies (> 50 kWh/kg H2) and limited industrial manufacturing capacity. Moreover, critical raw materials and other materials with sustainability or environmental concerns are used. To overcome these challenges, it is important to develop and invest in technologies that are expected to have competitive production cost (2-3 €/kg H2), increased efficiency (< 48 kWh/kg H2), improved durability.
X-SEED aims at developing an innovative alkaline membrane-less electrolyser working at supercritical water conditions (>374°C; >220 bar), generating high-quality H2 at pressures over 200 bar. This technology maximizes energetic efficiency, improves circularity, and enhances lifetime, resulting in a more competitive green H2 production. In X-SEED; novel catalysts and electrodes are designed, synthesized, and characterized to ensure high efficiencies. Results are validated at laboratory scale (TRL4) for a single cell and a 5-cell stack. Modeling and cell design ensure laminar fluid flows, allowing H2 and O2 separation employing a membrane-less electrolyser. Supercritical conditions and the membrane-less configuration reduce the electrochemical work required to generate H2 (decreased interface resistances ) and increase system lifetime. This results in an improved energy efficiency (42 kWh/kg H2, > 3 A/cm2), H2 production rate and robustness (degradation rate < 1%/1000h). X-SEED also integrates circularity and sustainability assessments in decision-making, limiting the use of critical raw materials (below 0.3 mg/W) and using wastewater for both catalyst production and electrolyte. The X-SEED consortium possesses extensive technical knowledge and experience in these key technologies. It will realize multiphysics models of cell and stack (DTU, SNAM, IDN, PMat), manufacture and select the best catalyst and electrodes (LEITAT, PMAT, IDN), and design the cell, the stack, and the test bench to validate the supercritical electrolyser at a laboratory scale (IDN, PMat, SNAM). The X-SEED project adds value beyond the technological dimension: It will accelerate the H2 ecosystem, support Europe in meeting climate targets and maintain its leadership position as a technological developer and producer of green energy.
