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

Vanadium-supported TiO₂ 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<i>H</i>, kJ·mol^-1) 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<i>H</i> of V-supported anatase was decreased from 10.13 to 4.13 kJ·mol^-1. At the same loading amount of 1 wt %, anatase showed a higher Δ<i>H</i> value of 8.71 kJ·mol^-1 than rutile and brookite. When the ratio of the {001} facet was increased in the anatase, Δ<i>H</i> was increased to 9.65 kJ·mol^-1. 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<i>H</i> stood for forming a more active V species during catalyst preparation, which further stood for a higher turnover frequency (TOF, s^-1) during the catalysis. The anatase with the biggest ratio of the {001} facet resulted in the biggest Δ<i>H</i> 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.