Enthalpy Change of V-Ti Interface as an Indicator of High Catalytic Activity.

Vanadium-supported TiO is one of the most widely used catalysts. In previous reports, most researchers focused on the performance of a formed catalyst and almost no work was devoted to understanding the activation process from a precursor to a catalyst. In this work, differential scanning calorimetry was used to calculate the enthalpy change (Δ, kJ·mol) during the transition from a precursor to a catalyst. When the V-loading amount was increased from 0.1 to 5 wt %, more polymeric V were formed and Δ of V-supported anatase was decreased from 10.13 to 4.13 kJ·mol. At the same loading amount of 1 wt %, anatase showed a higher Δ value of 8.71 kJ·mol than rutile and brookite. When the ratio of the {001} facet was increased in the anatase, Δ was increased to 9.65 kJ·mol. A theoretical calculation proved that V embedding into {001} facet resulted in a bigger energy difference in comparison to {101} and {100} facets. A bigger Δ stood for forming a more active V species during catalyst preparation, which further stood for a higher turnover frequency (TOF, s) during the catalysis. The anatase with the biggest ratio of the {001} facet resulted in the biggest Δ as well as the largest TOF. These results help to understand the interaction between loaded active species and catalyst support, which is in favor of designing an effective catalyst.