Thanks to the novel synthetic pathway, highly activated, defective, and clustered LDHs are obtained in a single-step fabrication. Among the 75 different LDH compositions (PGM-free) synthesized and characterised, 5 appeared as the most promising catalyst for the OER. An overpotential reduction range of 120-200 mV compared to bare nickel substrates was measured for these 75 compositions. The parent NiFe LDH with optimised ratio is complemented by the incorporation of other transition metals as alternative catalysts with lowest overpotential values of the electrochemical performance. The evaluation of the stability is focussed on the metal dissolution under operating conditions. With these powder catalysts, inks containing solvents and ionomers are coated with conventional processing techniques such as spray-coating, obtaining porous transport electrodes (PTEs).MATTECO has achieved a significant milestone by developing an innovative technology for up-scaling the production of catalyst layers, avoiding ink processing, which involves the direct growth of catalysts in PTEs, with no limitations in size or morphology.
Furthermore, the project tackles the optimization of the catalyst, support, ionomer, and separator interplay. Modifications of the cell design, like implementing bipolar membranes or the cell operation, such as changing the KOH/NaOH electrolyte concentration in the anode or working in dry cathode/anode conditions, will have strong impacts on the mass transport of the reactants and products directly influencing the cell performance. Moreover, by adapting a reported membrane-less electrolyser with a reference electrode, the catalysts and catalyst layer screening will be performed, splitting the kinetic and mass transport contributions to the total cell voltage of AWE from the cathode and anode separately. With respect to the in-situ characterization espectroelectrochemical Raman under industrially relevant current densities has been carried out for the first time, using the previously optimized catalysts. A new prototype of Raman cell is now under validation and potential commercialization evaluation by HORIBA.
The ultimate objective of this project is to achieve superior performance in 300 cm² 6-cell stack AWE electrolysers ‒to reach similar performance to state-of-the-art AEMWE‒ but still using cost-effective and stable diaphragms and separators. The assemblies will be first tested on single cells of 5 cm², then scaled to 25 cm², and finally to a 6-cell stack of 300 cm². Overall, the team's work offers a promising direction for developing cost-effective and sustainable catalysts and electrodes for water electrolysis, potentially increasing the adoption of technologies based on water electrolysis. It is important to stress that AEMWE fed with 1 M KOH is used as a reference for the consortia, and most of the developments achieved using this technology will be directly extrapolated to AWE. To overcome the significant limitation related to membrane instability, we will perform 300 cm² 6-cell stack testing only on optimized interfaces and using stable diaphragms or separators to ensure reliable results.
In overall, SEAL-HYDROGEN aims to overcome the main barriers that water electrolysis faces through the lab-scale development and validation of single cells in short stacks of 6 cells.
