Oxide Support Inert in Its Interaction with Metal but Active in Its Interaction with Oxide and Vice Versa.

Supported metal or oxide nanostructures catalyze many industrial reactions, where the interaction of metal or oxide overlayer with its support can have a substantial influence on catalytic performance. In this work, we show that small Pt species can be well stabilized on CeO2 under both H2-containing and O2-containing atmospheres but sintering happens on SiO2, indicating that CeO2 is active whereas SiO2 is inert in Pt-support interaction. On the other hand, Co oxide (CoOx) supported on SiO2 can maintain a low-valence Co2+ state both in air and during CO2 hydrogenation to CO, indicating a strong interaction of CoOx with SiO2. However, the CoOx overlayer has a weak interaction with CeO2 and is easily reduced to metallic Co during the CO2 hydrogenation reaction producing CH4. Thus, SiO2 is active, but CeO2 is inert for CoOx-support interaction, which is counter to the common sense from the Pt/oxide systems. Systematic studies in stability behaviors of Pt and CoOx nanocatalysts supported on various oxides show that the reducibility of the oxide supports can be used to describe the catalyst-support interaction. Oxide supports with high reducibility or low metal-oxygen bond strength interact strongly with Pt and other metals, showing high metalphilicity. Conversely, oxide supports with low reducibility or high metal-oxygen bond strength have strong interaction with CoOx and other oxides, having high oxidephilicity.