Increased nickel exsolution from LaFe0.8Ni0.2O3 perovskite-derived CO2 methanation catalysts through strontium doping

Perovskite-derived Ni catalysts offer the remarkable benefit of redox stability that allows their regeneration after deactivation through poisoning or Ni particle growth. Here, the catalytic activity of LaFe0.8Ni0.2O3 towards CO2 methanation was improved by increasing Ni reducibility and segregation to the perovskite surface through partial substitution of La by Sr (La1-xSrxFe0.8Ni0.2O3-delta, 0 <= x <= 0.1). Temperature programmed reduction, X-ray diffraction, scanning electron microscopy and X-ray absorption spectroscopy were used to characterize the materials, their stability against severe reduction at high temperatures and to quantify Ni segregation. It is shown that Ni reducibility was significantly increased (up to 50%) upon introduction of Sr, because more Ni was exsoluted during catalyst pre-reduction. Nickel reincorporation into the perovskite-type oxide lattice during reoxidation was not affected at these Sr levels and complete redox stability could be demonstrated for all compositions investigated in this work