Site-Selective CO2 Reduction over Highly Dispersed Ru-SnOx Sites Derived from a [Ru@Sn9]6– Zintl Cluster

Due to the unstable nature of isolated transition metals under real reaction condition, a systematic understanding on how much influence the isolated structure of the active site and the cofed chemicals have on fine tuning the selectivity toward specific reaction pathways is still lacking. Here, we show a combination of kinetic, thermodynamic, and in situ spectroscopy measurements to probe the rWGS and methanation of carbon dioxide on a CeO2-dispersed isolated Ru catalyst (Ru-SnOx/CeO2, structure confirmed by HAADF-STEM) derived from the [Ru@Sn9]6– Zintl cluster decoration. Kinetic measurements, in combination with isotopie-labeling reactions, prove that rWGS and methanation occur through the kinetically relevant C–O bond rupture of surface carboxyl (HOCO*) and surface formate (HCOO*) respectively. A site-selective reaction model has been established on the basis of the response of rWGS and methanation to water pressure. Probably, the rWGS was carried out at the interface between the transition-metal nanoparticles and the support and could be influenced greatly by water, while the methanation was carried out at a site far away from the interface and has a weak dependence on water. This system can be easily extended to some other hydrogenation reactions, thus attracting attention to building isolated structures with Zintl clusters.