Next generation of reversible proton conducting ceramic cells and stacks for efficient energy applications at ≥1 kW scale

Expected Outcome

The growing global energy demand coupled with the concerns about environmental pollution necessitates an increased share of renewable energy sources, implementation of C-free fuels and electrification of energy intensive industry. This calls for developing an efficient reversible proton conducting ceramics (PCC) technology capable of producing hydrogen and operate with hydrogenated fuels to reduce operational downtime and benefit from sector coupling. A flexible solution can be implemented with the use of proton conducting ceramic cells, which can selectively extract hydrogen from various gas streams through proton transport in the dense electrolyte at intermediate temperatures ranging from 450 to 750 °C. For instance, electrochemical proton conducting ceramics (PCC) are investigated for reversible steam electrolysis and hydrogen fed fuel cells, ammonia fed fuel cell, ammonia cracking to hydrogen, CO2 conversion to chemicals, dehydrogenation of hydrocarbons. Extensive research at the single cell level for these applications is showing that PCCs can produce, extract, purify, electrochemically compress, and use hydrogenated molecules as feedstock for power and/or chemicals production. While PCC cells are investigated in many applications, limited studies have been conducted on assessing the techno-economic potential of this technology for reversible operation.

There are several challenges to overcome to reach higher technological scales. The research work is primarily directed at cell level, which precludes the possibility for optimising thermal management. Reversible operation contributes to accelerated degradation in fuel cell mode, requiring more research on materials and cell assemblies, and their thermomechanical stability. In addition, there are challenges in developing reversible electrodes, which are equally active in both fuel cell and electrolysis modes. Improved electro-catalytic performance and faradaic efficiency have been observed when operating the cells in pressurised electrolysis or fuel cell mode. However, the mechanical integrity of the cells and traditional ceramic-based seals is difficult to maintain under these conditions (typically above 5 bar, and/or small pressure fluctuations).

Electrochemical devices integrating proton-conducting ceramics (PCCs) represent an emerging class of high-temperature energy systems. While conventional solid oxide cells (SOCs) rely on pure oxygen-ion conduction, PCCs transport protons either predominantly or in combination with oxide ions (co-ionic conduction) in some specific conditions through a dense ceramic electrolyte. The co-ionic electrolyte-based ceramic cells introduce simultaneous protonic and oxide-ion transport, enabling dynamic in situ water management across both electrode chambers. This dual ionic conduction opens new pathways for optimising electrode architectures and interfacial processes with the potential for significantly enhancing electrochemical performance, stability, and integration with downstream hydrogen and synthetic fuel production systems. PCC enables operation at lower temperatures ranging from 450 to 750 °C, offering significant advantages such as reduced thermally induced material degradation, lower system costs, and could improve compatibility with intermittent renewable energy sources. These attributes make PCCs highly promising for accelerating the transition toward more sustainable energy infrastructures.

Project results are expected to contribute to all the following expected outcomes:

• Development of reversible PCC technology that will enable the replacement of energy/emission-intensive thermal processes by electrochemical ones;
• Integration of PCC systems with renewable energy sources (e.g., solar or wind) to validate dynamic performance and grid-balancing capabilities;
• Reduction of CAPEX and OPEX of the PCC technology through innovation in cell and stack design, manufacturing, durability, and operational strategies;
• Evaluation of new business cases benefiting from reversible operation and/or multi-mode operation and/or fuel flexibility of the PCC stacks, contributing to paving the way for further scaling up and deployment of PCC technology;
• Contribution to the establishment of European leadership in reversible PCC technology with European supply chain of cells and stacks.

Projects should deliver a clear pathway for roll out of the technology and industrial uptake.

Project results are expected to contribute to the following objectives and KPIs of the Clean Hydrogen JU SRIA for 2030:

• Cell current density (at operating voltage and temperature): > 0.75 A/cm2
• Degradation rate of cell: < 1% /1000 hr in each operational mode
• Stack current density: > 0.5 A/cm2
• Degradation rate of stack: < 2.5% /1000 hr in each operational mode
• Faradaic efficiency: ≥ 84% in electrolysis mode

Scope

This topic focuses on the development of advanced protonic or co-ionic ceramic electrochemical cells and stacks for reversible application to improve performance and durability. This should take into consideration strategies for reducing and/or recycling critical and strategic raw materials at cell/stack level. All geometries (e.g. tubular or planar) and cell architectures are in the scope of the topic. The applications of hydrogen separation, and/or hydrogen pumping or related (either side of the PCC in reducing gas atmospheres) are not in the scope.

The proposals should focus on the development and validation of novel proton ceramic or co-ionic (dual transport of protons and oxygen ions) electrochemical cells and stacks, which operate reversibly in electrolysis and fuel cell mode with high efficiency and durability. The reversible technology should be integrated in various use cases (e.g., considering various sectors, use of different fuels for the fuel cell mode, integration with renewable sources, etc.). The proposals should demonstrate how the reversibility is beneficial to the selected user cases and establish how the performance and durability of both cells and stacks are affected by the cell/stack design and the operational strategies.

Proposals should go beyond the scope and ambition of previous European projects (e.g., eCOCO2[1], WINNER[2], PROTOSTACK[3], GAMER[4], HySPIRE[5], PEPPER[6], ECOLEFINS[7]) and should address:

• Innovations in design and manufacturing of materials, components and assemblies to improve performance, efficiency, and durability under reversible operation;
• The proposal should demonstrate how sustainability aspects - such as reduction of Critical and Strategic Raw Materials (CSRM) content or incorporation of recycling strategies - are addressed;
• Cell and stack design advancements to optimise operation under dynamic conditions, as well as optimisation of thermal management within the stack undertaken through both modelling and experimental validation to provide design guidelines for scaling-up the stack technology. Thermal management of the stack and analysis of thermo-mechanical stresses in the different operation modes (e.g. in fuel cell mode and electrolysis mode) at stack design shall be considered;
• Validation of the reversible operation in both fuel cell (power generation) and electrolysis modes involving hydrogen, and where relevant for the use case scenario, operation with other hydrogen carriers (e.g. ammonia), co-electrolysis or (de)hydrogenation processes, etc;
• Validation of cell and stack operation in testing conditions representative of the selected applications for 2,000 hr operation;
• Production of stacks with multiple repeating units;
• The reversible operation should be demonstrated at a minimum scale of 1 kW power class;
• Elucidation of degradation mechanisms at component, cell and stack levels with the support of modelling and/or advanced characterisation techniques;
• Techno-economic assessment of the reversible technology, demonstrating system-level feasibility, impact of thermal management and associated benefits in selected user cases;
• Evaluation of at least two use cases with assessment of the environmental impact. This includes environmental life cycle analysis (LCA), demonstrating added value, decarbonisation potential, and compatibility with future energy system scenarios.

Experimental activities are expected to start at the material and cell level and end at the stack level with validation under relevant operation conditions. Broad engagement of stakeholders across the value chain is encouraged to support the transition towards industrial deployment and to ensure alignment with market needs.

For activities developing test protocols and procedures for the performance and durability assessment of (reversible) electrolysers proposals should foresee a collaboration mechanism with JRC[8] (see section 2.2.4.3 "Collaboration with JRC"), in order to support EU-wide harmonisation. Test activities should adopt the already published EU harmonised testing protocols[9] to benchmark performance and quantify progress at programme level.

For additional elements applicable to all topics please refer to section 2.2.3.2.

Activities are expected to achieve TRL 4 by the end of the project - see General Annex B.

The JU estimates that an EU contribution of maximum EUR 3.00 million would allow these outcomes to be addressed appropriately.

Technology Readiness Level - Technology readiness level expected from completed projects

Activities are expected to achieve TRL 4 by the end of the project - see General Annex B.

[1] https://cordis.europa.eu/project/id/838077

[2] https://cordis.europa.eu/project/id/101007165

[3] https://cordis.europa.eu/project/id/101101504

[4] https://cordis.europa.eu/project/id/779486

[5] https://cordis.europa.eu/project/id/101137866

[6] https://cordis.europa.eu/project/id/101192341

[7] https://cordis.europa.eu/project/id/101099717

[8] https://www.clean-hydrogen.europa.eu/knowledge-management/collaboration-jrc-0_en

[9] https://www.clean-hydrogen.europa.eu/knowledge-management/collaboration-jrc-0/clean-hydrogen-ju-jrc-deliverables_en