Solid Oxide Electrolysis Cells (SOEC) are solid-state devices that play a pivotal role in the efficient conversion of renewable electrical power into fuels, making them a key technology for the green transition. The SOEC technology allows for the production of green hydrogen through steam electrolysis, as well as the operation of SOEC in co-electrolysis mode (i.e., electrolysis of H₂O+CO₂) to generate synthesis gas (CO+H₂). This gas can then be processed further into a variety of carbon-containing fuels.

To achieve high electrochemical performance and mechanical robustness of SOEC, it is essential to manufacture these ceramic solid-state devices to obtain a mechanically strong support layer, thin and gas tight oxide ion conduction electrolyte and porous electrodes having structures optimized to ensure the highest possible density of active sites for the electrochemical reactions e.g. large percolating triple-phase-boundary density in cermet-based electrodes like the often applied nickel/yttria-stabilized-zirconia based fuel electrode.

Advanced and complementary characterization techniques are needed for the further development and improvements of SOEC towards marked entry to ensure a high performing, reliable and long-term durable SOEC technology for production of green fuels. The characterization techniques include combinations of electrochemical characterization (e.g. impedance spectroscopy), element mapping (e.g. via EDS, Raman spectroscopy) and micro- and nano-structural characterization (e.g. via TEM, STEM, SEM, FIB-SEM/3D reconstructions).

At Topsoe, we’re constructing an SOEC manufacturing facility in Denmark, set to be operational in 2025. This facility will produce electrolysis cells, stacks and modules with a capacity of 500 MW per year. We’ve already announced the first agreement, a reservation of 500 MW capacity. However, in parallel with the up-scaling and commercialization of our TOPSOE™ SOEC electrolyzer technology, it is remains crucial to continue the R&D work on SOEC – cells, components, and stacks. In this perspective, this presentation will provide an overview of Topsoe’s expertise, results, and initiatives in the field of SOEC. This spans from studies of materials’ properties, electrode nanostructures as illustrated in Figure 1, to the electrochemical performance of cells and stacks, and the design of MW-sized systems. We’ll present examples of performance and durability testing  and will concluded with a status on Topsoe’s up-scaling of SOEC production capacity.

Figure 1: Example of electrode nano-structure characterization via TEM of Ni/YSZ based fuel electrode produced and tested at Topsoe [1].