EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Nanoporous perovskite solid solutions are versatile materials and well suited for the use in catalytical applications, due to their large surface and thus higher reactive area [1,2]. The combination of high surface areas and the use of electric fields provide an adequate tool to further improve the properties required for catalysis by controlling defect formation and mobility. It has been previously shown that electrothermal treatments in air can improve the catalytic properties of perovskite materials via cationic segregation and formation of oxygen defects [3].

In order to better understand the influence of the electric fields on the surface states of nanoporous perovskites oxides, we investigated La$_{0.1}$Sr$_{0.9}$TiO${_3}$ (LSTO) treated at high temperature with the assistance of electric fields under inert gas conditions. LSTO under oxygen poor atmosphere has metallic properties and is used as electrode in fuel cells. Therefore, electrothermal treatments could improve the reactivity of the material by imparting new defect species. Samples were prepared using a modified Pechini synthesis, which yielded perovskites with surface areas ranging from 5 m$^{2}$/g to 60 m$^{2}$/g [4]. After electrothermal treatments the samples were characterized using different spectroscopy and diffraction techniques to assess changes in defect structure and composition. For reactivity studies, CO oxidation was used as a test reaction.

Compared to electrothermal treatments under air, an increase in conductivity was observed already at very low temperatures (T = 300 °C). As shown by spectroscopy measurements the band gap of the materials decreases proportionally with the increase in surface area. After treatment with electric fields, the high surface area samples showed a higher proportion of O$^{-}$-species and also performed better in the catalytic tests. In conclusion, treatment using electric fields can decisively influence surface reactivity of perovskite oxides and thus offers exciting prospects for the further development of high-performance functional materials.