The production of sustainable and clean energy is one of the most important challenges of our time, and it has motivated a great amount of research work in very different areas. Hydrogen fuel cells are amongst the most promising environmental-friendly devices, but their full exploit requires to develop novel components that satisfy the requirement for practical, every day, application. Of crucial importance is to find conducting materials (electrolytes) which can work between 200 and 500 °C and which show high conductivity. Among others, proton conducting oxides with so-called perovskite structure have emerged as some of the best candidates as electrolyte materials in this temperature range. Yet, in order to design materials tailored for application, one needs first to gain a better understanding of how protons move and how the properties of the material influence the way protons move.
In this thesis, I investigated one of the most well-known groups of proton conducting perovskite oxides, BaZrO3 based materials, and another, novel, family of energy-relevant perovskite oxides, oxyhydrates BaTiO3-xHx. For the investigations I mainly used light- and neutrons-based techniques. The basic idea of these techniques is to send a beam, of light or neutrons, on a material, and to study how the beam is modified due to the interaction with it. In this way it is possible to obtain very important information about the position of the atoms (structure) and the way they move (dynamics) in the material.
I specifically looked at the relationship between local structure, i.e. the structure on nanometer scale, and the way hydrogen moves. This helped us to better understand the fundamental properties of proton conducting oxides, especially on the local scale, and how these are affected by the chemical composition of the materials. More generally, the novel insights provided by this work contribute to the understanding and further development of materials for energy application.