Final Report Summary - IONBEATHETEROMAT (Ion beam techniques for the sub-nanometric characterisation of advanced energy conversion heterostructured materials) The main goal of the project was the development of analytical protocols based on ion beam techniques for the analysis of advanced materials used for energy conversion applications, such as triple-junction solar cells and solid oxide fuel cells. The performance, efficiency and durability of such devices are strongly dependent on the morphology, the chemical composition and structure of the surface and near-surface of the materials. Furthermore, different phenomena taking place during materials processing and performance might also lead to significant changes at the outermost surface and interfaces, and hence, altering the catalytic efficiency (e.g. formation of secondary phases, diffusion, segregation, surface poisoning, etc). The combined use of state-of-the-art surface analysis techniques, namely time of flight secondary ion mass spectrometry (ToF-SIMS) and low-energy ion scattering (LEIS), has provided the synergy to obtain a better understanding of the relationship between surface and near-surface chemistry and structure and material’s functionality. The project presented a novel analytical approach and has involved the investigation of two main aspects for the successful application of this methodology. Firstly, the reliable application of ion beam techniques for materials analysis, especially when aiming for the quantification of the surface coverage, requires a detailed investigation of the fundamental aspects of the ion-solid interactions in order to avoid any misinterpretation of the results. Secondly, the analysis of the hetero-structured materials at the atomic scale represents a challenge that requires outstanding capabilities in terms of surface sensitivity and specificity. Therefore, the objectives of the research project were focussed on the optimisation of the analytical techniques to push their performance towards unprecedented limits and the application to advanced energy conversion materials.The project has provided a significant contribution to the fundamental understanding of the surface chemistry and the functionality of diverse energy materials. For instance, cathode materials for solid oxide fuel cells and electrolysers (SOFC and SOECs) undergo chemical modifications and re-structuring at the surface at operating conditions. The socio-economic impact is clear as this knowledge allows the design and development of new functionalised materials with improved characteristics in terms of efficiency and durability. Furthermore, this project has been based on the use of a novel facility that hosts one of the few instruments of its kind in the world and the first one installed in the UK, clearly consolidating UK and Europe as a leader in the application of this novel technology. In addition to the general benefit for society, the research results are beneficial to the worldwide academic community and industry concerned with energy materials and advanced analytical techniques for materials analysis and surface science. In terms of the research deliverables, the project yielded a significant number of international conference contributions (15) and invited talks (4), two articles already published and 5 manuscripts in preparation. An important effort was made to disseminate the results of this project, attracting a great interest from the research community from several fields (including materials science, analytical chemistry and applied physics), and leading to a large number of international and within the host institution.