Enhanced redox performance of LaFeO3 perovskite through in-situ exsolution of iridium nanoparticles for chemical looping steam methane reforming

Abstract

Chemical looping steam methane reforming (CL-SMR) can produce high-purity hydrogen without additional separation units. However, the low reactivity of LaFeO3 oxygen carrier towards methane restricts the overall process performance. To enhance the redox activity of widely used LaFeO3 perovskite, a small amount of iridium was introduced to LaFeO3. The presence of iridium significantly enhanced both particle reduction and oxidation, and the particle preparation pathways of oxygen carriers greatly affected the long-term performance. The overall enhancement from the incorporation of iridium was demonstrated by density functional theory calculations. Despite these beneficial effects of iridium addition, surface iridium species prepared by an impregnation method were severely aggregated during successive redox cycling, leading to deactivation of the particles. In contrast, B-site incorporation of iridium leads to the exsolution of IrOx nanoparticles anchored on the perovskite host as well as to enhanced redox stability, which is essential for the long-term operation of the chemical looping process.