GRAIN BOUNDARY ENGINEERING INNOVATIVE SOLUTIONS FOR IMPROVED IONIC TRANSPORT IN CERAMIC INTERFACES

Description

The rise in global demand for energy is becoming increasingly unsustainable for the environment. Technological solutions to efficiently manage and convert energy are pursued to address this issue. Solid Oxide Cells (SOCs) are one such solution, offering the ability to convert chemical energy from various fuel gases (Solid Oxide Fuel Cells – SOFC)and split water into hydrogen and oxygen or reforming CO2 into CO and O2 (Solid Electrolyte Electrolyzer Cells - SOEC). These cutting-edge devices are a logical choice for transitioning toward sustainable energy development. They are highly efficient and flexible and can support power-to-power processes. The structure of a SOC is roughly based on two porous electrodes separated by a dense electrolyte. Continuous innovation in materials and processing routes regarding SOC core elements is necessary to improve their performance, extend their lifetime, and reduce costs. The concept of SOCs strongly connects to goals 7 and 13 of the 2030 Agenda for Sustainable Development of the United Nations. The Gd-doped ceria (GDC) is a relevant oxide-ion conductor for developing SOC technologies. GDC has a crucial functionality as an electrolyte among all likely applicability in the system. The SOC performance depends on the internal electrical properties of GDC. The transportation of conducting species along or across the grain boundary (GB) emerges as a predominant factor influencing GDC overall properties. These GBs serve as either highly conductive pathways or high-resistive barriers, thus significantly impacting the performance and efficiency of the materials. Understanding and optimizing the charge transport mechanisms at the ceramic interfaces are determining for enhancing the functionality of this oxide for electrochemical systems. In line with this scenario, the goal of this project is the exploitation of the precipitation of intergranular phase, to generate (quasi) percolating fast ion conducting pathways. The capability of Gd3+ segregation within GB regions of GDC provides the desired inherent conditions. Local chemical reactions with external species, such as alkali metal salts, are the core subject of this possibility. In the GDC system, the influence of alkali metal salts as external agents is observed when they previously incorporated by mixing process in a precursor stage. Most recently, findings indicate the real possibility of local GB interaction even in sintered GDC through molten salts. Intergranular phase nucleation can be tuned using tailored one-pot synthesis and impregnation of salts on dense ceramics. The simplicity of this approach is evident, considering that standard investigation on fast-conducting intergranular phases uses the combination of various elements and the formation of complex interphases. Furthermore, moving from complex explanations, the GB electrical properties of GDC co-doped with alkali metal cations suggest boosted ionic transport properties considering specific circumstances. Up to now undisclosed, the GB intergranular phase features are seemingly a possibility for observed improvements. The construction of this intergranular phase is pursued in this project. Studies on the relationship between processing routines and specific thermal treatments involving various molten salts with GB intergranular phase composition must be performed. This enables identifying ideal conditions to promote (quasi) percolated impacting phases. This must be complemented by adequate structural, microstructural, and electrical characterization with due feedback between performance and processing routes. Identifying prime conditions regarding materials interaction, phase formation, and species conducting mechanism is the relevant aspect to be raised. In fact, while one of the general procedures is relatively known, the impregnation processing findings are relatively new and scarcely studied. The adequacy of all the above-mentioned requisites to obtain materials with improved ionic transport is the challenge in this project. As a side stream activity, the project also includes the potential exploitation of research results based on the critical involvement of skilled international researcher consultants. Their expertise in SOC development will be an asset to obtaining insights concerning the technological and scientific components.