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

Nanoparticle exsolution from perovskite oxides has recently received great attention, due to the ability to generate perovskite supported nanoparticles with superior metal-support interaction and coking resistance. The introduction of A-site vacancies in the perovskite lattice has also been shown to increase the population and dispersion of the exsolved nanoparticles. Furthermore, the formation of NiFe alloys can be of particular importance for the reaction between ethane and CO2, since it has been found that Ni rich and Fe-rich alloys can favour the dry reforming and the oxidative dehydrogenation pathway respectively. In this work, we prepared A-site stoichiometric and A-site deficient La0.4Sr0.6 αTi0.6Fe0.35Ni0.05O3±δ (LSTFN) perovskites (α: extent of A-site deficiency) with a high surface area via a modified Pechini synthesis. The introduction of A-site deficiency was found to drastically promote the reducibility of the perovskite, as observed through H2-TPR, and the exsolution of NiFe alloy nanoparticles as evidenced by XRD and STEM EDS. Furthermore, the presence of Ni appears to drive the exsolution of Fe cations from the perovskite lattice due to the favourable thermodynamics of the NiFe alloy formation. The catalytic activity of the resulting catalysts, that comprised of exsolved NiFe alloy nanoparticles supported on mesoporous perovskite supports, was evaluated for the reaction between ethane and CO2. The catalysts were found to be fairly active, but stable, while they also favoured the dry reforming pathway and the scission of C-C bonds, compared to the oxidative dehydrogenation pathway that produces ethylene. According to the literature, this limited ethylene selectivity can also serve as an indicator that the exsolved alloy nanoparticles are rather Ni-rich. The perovskite with the highest A-site deficiency (α = 0.2), that had the largest population of exsolved NiFe alloy nanoparticles, was found to be more active compared to the A-site stoichiometric one.