Advanced materials for solid oxide fuel cell anodes produced by magnetron sputtering

Steier, Katharina (2025) Advanced materials for solid oxide fuel cell anodes produced by magnetron sputtering. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

The present global energy problems stem from environmental pollution caused by the world’s ongoing energy generation from fossil fuels. To ensure a clean and sustainable future, it is essential to use energy conversion systems that are both environmentally friendly and efficient, such as Solid Oxide Fuel Cells (SOFCs). SOFCs convert the chemical energy stored in fuels like hydrogen or gaseous hydrocarbons, directly into electrical and thermal energy. The efficiency and performance of SOFCs are inextricably linked to the material properties of the electrodes and the electrolyte. These properties are influenced by the nature of their microstructure, such as the percolated paths of their ionically and electronically conductive phases, the porosity, and most importantly, the grain size. As finer particle sizes in SOFC anodes increase the number of reaction sites, leading to higher performance, magnetron sputtering has been chosen in this work to develop advanced materials for SOFC anodes with enhanced properties in terms of efficiency and cost. A reactive feedback control system was applied to manage quantities of oxygen introduced during the deposition of yttria-stabilised zirconia (YSZ) as well as NiO-YSZ thin films based on the oxygen partial pressure. This facilitated stable operation conditions and controlled the coating characteristics, i.e., its microstructure and desired composition while varying process parameters, such as the deposition pressure or the substrate temperature during deposition. Both, the deposition at higher temperatures as well as at lower deposition pressures, resulted in densification of the microstructure of the deposited layers and a consequent loss of performance. In contrast, deposition at high total pressures resulted in significantly higher performance comparable to commercial SOFCs. After defining the optimal process parameter to create catalytically active Ni-YSZ films, complex oxides of vanadium and manganese were incorporated as dopants into the Ni-YSZ films in this work. The study found that the high dopant concentrations of vanadium or manganese resulted in significant performance degradation, showing structural and morphological changes in the doped Ni-YSZ films compared to undoped Ni-YSZ. This work will continue in the future to advance the state of SOFC anodes by lowering dopant concentrations or developing a graded composition in the film. The substitution of YSZ for an alternative electrolyte material, such as gadolinia-doped ceria represents another promising approach regarding the doping of Ni-based anodes.