The project initially evaluated a class of single-phase lanthanum strontium cobaltite La1-xSrxCoO3-d (LSC) materials, La0.6Sr0.4CoO3-d (LSC64) and La0.8Sr0.2CoO3-d (LSC82), as air electrodes for SOCs. The crystallinity of the films was studied as a function of substrate temperature during pulsed laser deposition and post-thermal annealing. Three crystalline states, i.e. fully crystalline, partly crystalline, and amorphous films, were chosen for further studies. Chemical activities and elemental distribution of the films subjected to long-term stability tests and the as-prepared films were compared. Our investigations on LSC64 films revealed that less crystalline films were not catalytically active for low-temperature (400 °C) SOC operation. At intermediate temperatures (500 and 600 °C), a comparable activity was measured for both fully crystalline and partly crystalline films. However, the degradation rate of the partly crystalline film was two times slower than the fully crystalline one for 100 h of testing. Based on all the findings, we determined that initial microstructural features of the films such as grain size, grain orientation and topography determine the cation segregation behaviour and thus the long-term catalytic activity.
In the second part of the project, vertically aligned composite nanostructures (VAN) comprising two materials known to show exceptionally fast electrokinetics for low temperatures operations were selected. This was a combination of an electronically conducting Ag metal and an ionically conducting oxide Ce0.9Gd0.1O2 (GDC). The Ag-GDC VAN films were deposited epitaxially on oriented yttria-stabilized zirconia substrates by PLD. Preliminary results show successful growth of ~40 to 400 nm thick oriented Ag/GDC VAN films. Both phases grew homogeneously and epitaxially on the substrate. in situ Raman spectroscopy was used to probe the stability of the films under airflow from room temperature to 400 °C. Initial findings indicate resistance to oxidation of Ag up to 400 °C and microstructural integrity up to ~350 °C. Additionally, we were able to show that the addition of GDC stabilized Ag by surrounding it through vertically grown columns.
For the exploitation and dissemination of the project, various activities such as publishing research articles, scientific talks at conferences and meetings, and participation in public engagement events were carried out. In terms of publishing, 2 peer-reviewed articles and 2 proceedings papers were published. At least 2 more peer-reviewed articles linked to INSPIRE and an invited chapter contribution to an e-book on nanoengineering methods developed and utilized for SOC air electrodes will be produced. In terms of scientific engagements, oral and poster presentations were given in the following conferences: Solid State Ionics (SSI), PyeongChang Korea in June 2019, European SOFC and SOEC Forum (EFCF) (virtual talk) in October 2020 and Electrochemical Society (ECS Prime) (virtual talk) in October 2020. Additionally, invited talks were given in the UK Surface Analysis Forum (UKSAF) in London, UK in January 2020, and STFC Batteries Early Career Researcher Conference in Oxford, UK in March 2019. In terms of public engagements, the principal investigator participated in the European Researcher’s Night in London, UK in September 2019.
