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

Abstract

Vanadium-supported TiO 2 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 (ΔH, 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 ΔH 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 ΔH value of 8.71 kJ•mol −1 than rutile and brookite. When the ratio of the {001} facet was increased in the anatase, ΔH 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 ΔH 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 ΔH 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.