Advancements in glass-ceramic sealants for proton conductive electrolysis cells (PCECs)

In response to the escalating levels of CO2 and other greenhouse gas (GHG) emissions, countries worldwide have recognized the critical need for a more sustainable system. To tackle this global crisis, governments are increasingly implementing new laws and strategies that prioritize the utilization of renewable energy technologies. However, one of the key challenges associated with these solutions is their intermittency, highlighting the necessity for efficient energy storage systems and solution for the overproduction period. In the last years, the utilization of hydrogen as a viable energy vector has become a pivotal driving force behind the ongoing energy transition towards a low-carbon future. Electrolysis of water, specifically green hydrogen production, offers a means to generate hydrogen by splitting water molecules using electricity, with the resulting hydrogen that can be after utilized as a fuel to generate electricity. In this context, high temperature cells have high efficiency, due to the elevated temperature that helps transport mechanisms. Solid Oxide Cells (SOCs) and Proton Ceramic Cells (PCCs), with a temperature range of 700-1000°C and 500-700°C, respectively are part of this family. While SOCs currently represent the most advanced technology, their primary drawback lies in the degradation issues stemming from their high operational temperature range. To address this concern, PCCs, which rely on proton-conducting electrolytes, present a promising solution by reducing operating temperatures while maintaining high efficiency and cost-effectiveness. PCECs are now mainly at laboratory scale, so more efforts are needed to develop stack of large area cells with commercial interest. This thesis aims to improve the knowledge on this open issue, focusing on the characterization of the sealant material. The sealant is a crucial component in this technology as it prevents gas leakage or diffusion within the stack. In the case of the presented study, glass-ceramic sealants were considered. The characterization process included both the thermo-mechanical and chemical aspects of the sealant material, like the compatibility with the other component of a stack of cells (electrolyte, electrode, and interconnector), and the behaviour of the selected material at the operational temperature (500-700°C). Additionally, further studies were made, preparing glass pastes and analysing their rheological properties, in terms of printability and shape-fidelity. This was done for evaluate the feasibility to use a robocasting deposition method, which establish the foundations for industrial scaling of the production. After that, studies on electrochemical characterization and simulation modelling were conducted, with the aim to create and validate a benchmark model of a PCEC. That was made using COMSOL Multiphysics software, for the simulation part, calibrated with data from literature.