Protonic Ceramic Membranes: Up-Scaling and Application to E-Fuels Synthesis
Authors: Dailly Julian , Schmider Daniel , Blanck Philipp , Marrony Mathieu , Deutschmann Olaf 
Published: December 2024

Abstract

The production of synthetic fuels / chemicals relies on the availability of the reactants: low-carbon H2, CO2 valorization from various CO2 sources, N2. In addition, the value chains are not enough mature to be considered as commercial and still need improvement. The main levers are high production costs of conversion processes, access to biologic or fatal CO2 sources and issues related to the H2 supply chain (H2 cost, heat recovery, etc.). The main streams for improving current e-fuels conversion technologies being explored by industry are focused on new catalyst materials and new reactor architectures to enhance CO2 / N2 and H2 conversion and selectivity towards the desired molecule.
However, new low TRL innovations are developing around protonic ceramic-based technology. It offers the advantage of being able to intensify the process by integrating hydrogen supply (electrolysis of water, then transfer of protons through the membrane) and conversion to the desired molecule (catalytic effect) in the same electro-catalytic reactor. Based on its extensive experimental and collaborative experience, EIFER is now focusing its research in the ENERMAT laboratory on the development of protonic ceramic cells for a variety of applications, including NH3 production and the direct conversion of CO2 into CH4, up to the integration in an SRU/stack environment.

Manufacture and characterization of samples

Using a multi-step manufacturing wet chemical route, hydrogen electrode supported samples from 10 to 50 cm² have been achieved. The hydrogen electrode substrate is firstly manufactured by tape-casting from a slurry containing NiO and BaCe1-x-YZrxYyO3-δ (BCZY). The BCZY-based electrolyte is coated by screen-printing, and the bilayer assembly is co-sintered at a temperature around 1300°C to limit the effect of shrinkage and diffusion. The last electrode layer is also coated by screen-printing and fired at a lower temperature to keep its structure and ensure a good bonding with the membrane.
The final microstructure results in a thin (below 10 µm) and dense membrane, whereas the electrodes remain porous to ease the gas diffusion. In order to enhance the activity of samples, catalysts are either infiltrated or directly incorporated in the electrode layer(s). As an example, the figure 1 shows the composition of a protonic ceramic multilayer assembly for the synthesis of ammonia. The iron catalyst is introduced into a sintered backbone layer by infiltration or by direct embedding into a composite structure.
The multi-layered assemblies are tested in adapted laboratory-scale reactors. The gas produced are analyzed using mass spectrometry and the electrochemical behavior of the samples is analyzed by impedance spectroscopy. Finally, the microstructure of the layers is observed and compared before and after electrochemical measurements.
Here, EIFER’s main achievements for the manufacture of large multi-layered assemblies and the synthesis of hydrogen derivatives will be discussed.

Figure 1