Development of iron-nickel containing perovskites with increased oxygen carrier capacity for chemical looping H2 production

Modifications of the perovskite La0.6Sr0.4FeO3-δ (LSF) using different amount of Ni replacing Fe in the LSF lattice have been synthesised, tested and fully characterised under cyclic redox conditions in the temperature range of 600-900 °C. The results are compared with reference LSF material in terms of material and process performance. X-ray diffraction characterisation results showed that the increase of Ni content leads to the general formation of LaxSr1-xFeyNi1-yO3 species; at higher Ni doping, the formation of multiple perovskite species, and the formation of Ruddlesden-popper perovskite (La0.3Sr0.7)2FeO4. The best performance of cyclic stability was achieved with La0.6Sr0.4Ni0.33Fe0.67O3-δ exhibiting only a 3% capacity drop over 20 cycles, while a larger drop in capacity (33% for La0.6Sr0.4Ni0.5Fe0.5O3-δ and 6% for La0.6Sr0.4Ni0.1Fe0.69O3-δ) was obtained with other materials due to structural breakdown, sintering, and carbon deposition. Overall, an increase of 2.3 times of oxygen carrier capacity was recorded compared to La0.6Sr0.4FeO3 during oxidation with steam, resulting in 0.743 mmolH2/goc hydrogen yield at 900°C at a 55% H2O conversion. The total oxygen capacity increased with Ni doping due to structure modifications which increased the oxygen active sites available. In the case of reduction with CO, the same material did not show carbon deposition, sintering, or structural breakdown. Furthermore, long term stability has been confirmed by performing 100 redox cycles in a thermogravimetric analyser, with H2 as the reducing agent.