The REDHy project tackles the limitations of contemporary electrolyser technologies by fundamentally reimagining water electrolysis, allowing it to surpass the drawbacks of state-of-the-art (SoA) electrolysers and become a pivotal technology in the hydrogen economy. The REDHy approach is highly adaptable, enduring, environmentally friendly, intrinsically secure, and cost-efficient, enabling the production of economically viable green hydrogen at considerably increased current densities compared to SoA electrolysers. The REDHy method is based on the findings of numerous EU-funded initiatives and patented by the DLR (TRL2). Unlike SoA electrolysers, REDHy is entirely free of critical raw materials (CRM) and doesn't require fluorinated membranes or ionomers, while maintaining the potential to fulfil a substantial portion of the 2024 KPIs. The project's ultimate objective is to create a prototype, validate it in a laboratory setting for 1200 hours at a maximum degradation of 0.1%/1000 h and achieve TRL4. This final phase will emphasize the potential of the REDHy approach and its crucial role in the upcoming hydrogen economy, secure subsequent investments, and showcase the necessity for ground-breaking, innovative thinking to reach climate objectives in a timely fashion. As the world grapples with a climate crisis marked by increasingly frequent and severe natural disasters, it has become essential to transition from our reliance on fossil fuels to cleaner, greener energy sources. Green hydrogen, with its potential to decarbonize a range of sectors including transportation, power generation, and carbon-intensive industries, has emerged as a key player in this energy revolution. Although water electrolysis holds significant promise as a sustainable means of producing green hydrogen, it has not yet taken center stage in the hydrogen production landscape, despite decades of research and development efforts. As experts continue to explore the potential of this innovative technology, it is crucial to overcome the current limitations and unlock its full potential in order to accelerate the shift towards a decarbonized future. However, the SoA electrolysers, which include polymer electrolyte membrane water electrolyzers (PEMWE) and alkaline water electrolyzers (AWE), present challenges in terms of capital costs, efficiency, scalability, safety, durability, electrical grid reliance, ultra-pure water requirements, and dependence on CRMs (EU CRMs list2020). These limitations cast doubt on whether water electrolysis can ultimately become the leading technology for truly green hydrogen production, potentially delaying the urgent transition to clean energy carriers. Recognizing the need to address these considerable challenges and unlock the full potential of green hydrogen as an energy carrier, it is clear that a radical rethinking of electrolyzer technology is essential. In response to this need, we present the REDHy project, which introduces a groundbreaking and efficient approach to green hydrogen production that transcends the limitations of state-of-the-art electrolysers.
The REDHy technology presents an enthralling alternative pathway for green hydrogen production, employing a series of cutting-edge innovations to create a more economically viable process. Utilizing redox mediators and nano-engineered heterogeneous catalysts in conjunction with 3-D electrodes, the technology separates anode and cathode reactions, ultimately enhancing electrolysis safety and cell performance. Separating the gas evolution from the actual system allows hydrogen production outside the building, which increases the safety and acceptance of electrolysis. By focusing on the kinetically preferred water-dissociation step and redox mediator reactions, REDHy bypasses the sluggish electrochemical water splitting process, resulting in lower overpotential and the use of low-cost materials free of CRM. These advancements pave the way for high catalyst utilization and the elimination of the need for a typical hot-pressed membrane electrode assembly, thereby simplifying manufacturing methods. Furthermore, the REDHy technology is capable of integrating disruptive concepts from various fields, giving rise to an innovative cell design that boosts overall system efficiency through optimized heat and simplified safety management. Notably, the technology also permits the use of seawater as opposed to ultra-pure water for green hydrogen production. With this in mind, it is evident that REDHy is not only an elegant solution offering a simpler and less demanding path to green hydrogen production, but bears a high potential to become the future electrolyser technology delivering economic and truly green hydrogen. REDHy’s main objectives are:
1: Develop highly efficient and durable materials free of critical raw and fluorine free materials for the REDHy technology, especially the membranes, ionomers, electrodes, redox mediators, and heterogenous oxygen and hydrogen evolution catalysts to allow the development of a short stack (5 cells) with an active surface area of >100cm2/cell and a nominal power of >1.5 kW with adequate manufacturing quality guided by Europe's circular-economy action plan
2: Validate the stack's efficiency and robustness to address dynamic situations frequently occurring when the electrical grid is fed by a large proportion of renewable energy sources or if the system is directly interfaced with RES
3: Eliminate the use of and the need for critical raw materials and fluorinated membranes and ionomers at stack level
4: Demonstrate optimization strategies for the porous electrodes to enhance their mass transport characteristics and enhance energy efficiency
5: Demonstrate a reduced energy consumption of at least 48 kWh*kg-1 H2 by implementing highly reversible, stable redox mediators with enhanced kinetics
6: Demonstrate a drastic reduction in interface resistances across all cell components leading to energy efficiencies >82%
7: Demonstrate the decoupling of oxygen and hydrogen production and enabling the REDHy system to operate at minimum 5% of partial load operation (nominal load 1.5 A/cm2) without exceeding 0.4 % of H2 concentration in O2
8: Demonstrate that the REDHy technology is capable to perform efficient and direct seawater electrolysis
9: Integrate the short stack in a prototype full system
10: Demonstrate the operation of the REDHy electrolyzer at 1.5A*cm-2 with electricity consumption of 48 kWh*kg-1 over at least 1200 hours of operation with a degradation of 0.1 % /1000 h
