Nickel nanocatalyst exsolution from (La,Sr) (Cr,M,Ni)O3 (MMn,Fe) perovskites for the fuel oxidation layer of Oxygen Transport Membranes

La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) and La0.75Sr0.25Cr0.5Fe0.5O3 (LSCF) perovskites with partial substitution of the B-site by 5 mol% of Ni were synthesised and characterised for the fuel oxidation layer of Oxygen Transport Membranes (OTMs). X-ray diffraction showed that single phase compounds were obtained at 1300 °C. LSCM exhibits a rhombohedral structure and LSCF an orthorhombic structure. Both materials retain their structures, after doping the B site with Ni, with small changes on the unit cell parameters. Thermal analysis under reducing conditions was used to investigate the reducibility of these perovskites up to 900 °C, which appears to be enhanced by doping with Ni. The formation of Ni nanoparticles (30-50 nm) on the LSCMNi and LSCFNi grains was observed by scanning electron microscopy, after reducing the samples in 5% H2/Ar at 900 °C, indicating possible enhanced catalytic activity and potential benefits for the development of the OTMs. DC conductivity measurements conducted under a redox cycle, indicate that LSCFNi presents a better redox stability than LSCMNi.