In situ exsolution of Rh nanoparticles on a perovskite oxide surface: Efficient Rh catalysts for Dry reforming

Abstract

The catalytic activity of the Rh-exsolved Sr0.92Y0.08Ti2O3−δ- perovskite catalyst (SYTRh5) was examined for dry reforming of methane. The exsolution of the Rh nanoparticles over the SYT perovskite oxide surface was carried out under various reducing environments where the extent of Rh exsolution was significantly determined by the reduction time (4, 12, 24 h) and temperature (800, 900, 1,000 °C). STYRh5 catalysts treated at a longer reduction time and a higher reduction temperature revealed formation of larger metallic Rh nanoparticles on the perovskite oxide with higher surface concentration. For dry reforming activity, the SYTRh5 catalysts reduced at 900 and 1,000 °C for 24 h showed significantly higher methane conversion compared to others. The high catalytic performance of the SYTRh5 (900 and 1,000 °C, 24 h) catalysts was attributed to the high coke-resistance of the larger Rh-exsolved nanoparticles and stronger anchoring sites resulted from the exsolution process. Post-analysis TEM images exhibited limited carbon deposition and particle agglomeration of Rh over the SYTRh5 (900 and 1,000 °C, 24 h) catalysts. Lastly, in-situ H2S poisoning was conducted to examine the regeneration ability of SYTRh5. Although catalyst deactivation was observed, the catalytic activity of SYTRh5 (900 and 1,000 °C, 24 h) was completely recovered to the original level once the H2S flow was interrupted, indicating facile desorption of sulfur species from the Rh-exsolved nanoparticles.