Surface property tuning of LaCr0.7Ni0.3O3 based perovskite catalysts enable efficient operation of SOFCs on liquid fuels

Abstract

A-site Sr or Ca substituted perovskite LaCr0.7Ni0.3O3 (LSCN, LCCN) are prepared in this work as catalysts of simulated diesel fuel (N-hexadecane) steam reforming for the on-board hydrogen supplement of solid oxide fuel cells (SOFCs). The effect of different dopants on active metals dispersion and surface properties on catalyst performance is analyzed. The results of the investigation reveal that LCCN possesses the highest catalytic activity coupled with exceptional stability, achieving full fuel conversion at WHSV = 5 mL/g·h, S/C = 3.0, and 750 °C and keeping stable for 200 h, thereby emerging as a potential candidate for liquid fuel processing. SEM, H2-pulse chemisorption and XPS results confirm that the excellent performance is due to the high metal dispersion and steam activation capacity. The poor catalytic performance observed in LSCN is primarily attributed to the presence of Sr segregation and the formation of the SrCrO4 second phase. Sr segregation decreases the steam activation ability of the catalyst as confirmed by XPS. DFT calculation also shows that Sr dopant and Sr segregation decrease the exsolution trend of metal Ni in the perovskite matrix, leading to poor metal dispersion. A simulated reforming gas is used in SOFC and the cell can keep stable for 120 h at a discharging current density of 0.4 A/cm2. This study analyzes the difference between Ca and Sr dopants, and reveals the detrimental effect of Sr segregation, which could enlighten the effect of surface tunning on the performance of perovskite catalysts.