NOVEL ELECTRODE COATINGS AND INTERCONNECT FOR SUSTAINABLE AND REUSABLE SOEC

Project Information

NOUVEAU

Grant agreement ID: 101058784

DOI

10.3030/101058784

Project closed

EC signature date 24 May 2022

Start date 1 September 2022

End date 30 November 2025

Funded under

• Digital, Industry and Space

Total cost

€ 3 880 640,75

EU contribution

€ 3 880 638,75

Coordinated by

VLAAMSE INSTELLING VOOR TECHNOLOGISCH ONDERZOEK N.V.
Belgium

Periodic Reporting for period 1 - NOUVEAU (NOVEL ELECTRODE COATINGS AND INTERCONNECT FOR SUSTAINABLE AND REUSABLE SOEC)

Reporting period: 2022-09-01 to 2024-02-29

Summary of the context and overall objectives of the project

Renewable energy sources such as wind and solar power are important for the sustainable energy supply to replace the fossil fuels and to mitigate climate changes. These renewable sources require storage and conversion devices to overcome their non-constant energy supply. In this frame, Solid Oxide Electrolysis Cell (SOEC) technology is a key technology for the ongoing energy transition towards a low carbon future. It is the most viable route for the efficient utilization of renewable electricity to produce green hydrogen and fuels. SOEC technology benefits from the easier availability of the oxide materials involved, compared to polymer electrolyte membrane fuel cells (PEMFCs) that are based on expensive Pt electrodes. In addition, SOEC has the advantages of efficiency and compactness, as well as the ability to produce synthesis gas directly, compared to the traditional low temperature alkaline electrolyzers as well as PEM based electrolyzers. The commercialization of SOEC technology is just starting to take off, with more companies entering the market and establishing mass-production capabilities to decrease the cost per kW. The electrolysis capacity is about 2 GW in 2020 and is expected to increase to at least 10 to 60 GW/year by 2030.
However, for the cell manufacturing, SOEC are currently using several rare earth elements (REE) such as Y and La, which is not convenient as Europe is strongly dependent on REE import. Moreover, the largest cost of SOEC is now caused by the stainless steel interconnect. Interconnects are a crucial part of SOEC to connect the different cells, but it suffers from Cr retention and corrosion, which lead to degradation of the SOEC.
In this context, NOUVEAU project will create a more sustainable and less expensive SOEC system technology that is scalable for the electrochemical production of hydrogen as a renewable fuel from steam and renewable electricity. More specifically, NOUVEAU will focus on three main components of the SOEC research: i) REE-reduced oxygen electrode, ii) Cr-reduced interconnect and ii) recycling possibilities of the electrolyte. To achieve these objectives, NOUVEAU will employ innovative coating methodologies and modelling, in combination with sustainable-by-design aspects and recycling options.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In the first part of the project, activities have focused on all the three SOEC research areas.
To reduce the amount of REE, specifically La, in the oxygen electrode, several La-free electrode materials were synthesized and characterised on lab-scale, such as compositions deriving from Ca2Fe2O5 brownmillerite. Besides the novel compositions, diverse coating methodologies (spray coating and up-scalable slot die coating) are explored to optimize the microstructure of the electrode, vital for improving performance and durability. Furthermore, environmentally friendly green inks are being developed for the oxygen electrode, highlighting the project's commitment to sustainability. For these methodologies, one of the La-free electrode materials was already successfully manufactured at kilogram scale.
This experimental work is supported by modelling, which will allow to predict, assess and characterize specific properties of novel compositions for electrode coatings at the early stage of experimental design. This approach will reduce time and costs of experimental research. The first NOUVEAU database was developed to describe and characterize the possible SOEC structures and their physicochemical parameters, which are crucial for designing the oxygen electrode. This database was developed based on collected literature data and will be extended during the project by theoretically generated structures and quantum mechanical calculations as well as by experimental data provided by the NOUVEAU consortium.
For the development of a metallic interconnect, consisting of a stainless steel component and a protective coating, with reduced content of Cr and reduced cost compared to the state-of-the-art material Crofer 22 APU with an atmospheric plasma sprayed (APS) coating, suitable stainless steel substrates were selected. So far, a dense and homogeneous protective coating has been deposited on Crofer (as benchmark) and two alternative metals, AISI441 and AISI430, using APS. In addition, an alternative coating technique, electrophoretic deposition (EPD) is being explored as a more scalable technology than APS. Oxidation testing of the bare and coated steels is currently ongoing.
The recycling of the electrolyte is also considered in the life cycle sustainability assessment of the defined NOUVEAU system. An important step for the recycling task of the electrolyte, is the separation of the interlayer GDC and the electrolyte YSZ. A technique for this was elaborated by leaching GDC without YSZ. Further steps in the recycling process will be investigated in the next period.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The developed SOEC system by NOUVEAU is expected to be much more sustainable and less costly than the state-of-the-art SOEC.
By reducing the amount of La (REE) in the solid oxide cells by min. 30 % and by recycling the yttrium of the electrolyte material, the dependency on REE and the energy demand for mining these materials will be significantly reduced. Furthermore, the switch to green inks for the electrode applications will lead to eco-friendly processing of SOEC compared to the current solvent based systems.
The Cr reduction in the interconnect steel by min. 20 % will have the largest positive impact on the cost of the SOEC. Furthermore, the more efficient coating methodology in combination with water-based inks will further enhance the economic advantage of the NOUVEAU outcomes.
A full sustainability assessment, including environmental, social, economic, eco-efficiency, criticality and circularity indicators, in combination with the safety assessment, will be performed as part of the project to validate these claims, as an important lever towards industrial implementation. The resulting life-cycle profiles will serve as guideline for other metallic coatings and engineered surfaces (e.g. fuel cells and batteries).