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 (CoO<i>_x</i>) supported on SiO₂ can maintain a low-valence Co²⁺ state both in air and during CO₂ hydrogenation to CO, indicating a strong interaction of CoO<i>_x</i> with SiO₂. However, the CoO<i>_x</i> 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 CoO<i>_x</i>-support interaction, which is counter to the common sense from the Pt/oxide systems. Systematic studies in stability behaviors of Pt and CoO<i>_x</i> 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 CoO<i>_x</i> and other oxides, having high oxidephilicity.