Variable Temperature STM Investigations on the Role of Ti Interstitials in Methanol Chemistry for Mass-Selected VO Clusters supported on TiO₂ (110)–(1x1)

Mixed-metal oxides display unique catalytic properties that are distinct in their reactivity and selectivity from either parent metal oxide. This is attributed to the novel electronic structure and local bond-coordination present at the interface between both metal oxides. Thus, understanding the role of each metal oxide has on the interface is critical to improving their catalytic properties towards industrially relevant reactions. In particular, the selective oxidative dehydrogenation of alcohols and alkanes over VOx supported on TiO₂ have been studied extensively over the past three decades, due to their high selectivity and affordability over Pt based catalysts. A combination of variable-temperature STM and temperature programmed desorption/reaction, reveal that methanol oxidizes the reduced TiO₂ (110) surface occurs via Ti interstitial defect sites that diffuse from the bulk. In the presence of isolated, well-defined VO clusters on the surface, Ti interstitials are attenuated and reactivity towards methanol is modified. The VO/TiO2 interface investigated here represents an interesting model towards understanding the synergistic effects of mixed-metal oxides.