Dependence of the strong metal-support interactions of Ni/TiO2 and the induction period of glycerol steam reforming on the dynamic crystal phase evolution

The dynamic relationship of TiO2 crystal phase and strong metal-support interactions (SMSI) of Ni/TiO2 catalyst was investigated to reveal the induction period of glycerol steam reforming. Comprehensive investigations confirmed that the SMSI between Ni0 and anatase TiO2 was formed by anatase TiO2 encapsulated Ni0 after H2 reduction at 500 °C for the Ni/TiO2 catalyst calcined at 500 °C (Ni/Ti-500R), which inhibited the contact of Ni0 active sites with reactants and led to the low hydrogen yield in the initial stage of the reaction. Interestingly, the dynamic conversion of anatase to rutile during the GSR process at 600 °C caused the TiO2 overlayers on the Ni0 particles to gradually fade, exposing more Ni0 sites, resulting in a gradual increase in hydrogen yield to 5.93 molH2/molglycerol. In addition, Ni/Ti-500R with a dynamic SMSI inhibited Ni0 particles sintering and encapsulated carbon deposition, resulting in relatively better stability (21 h) after induction period. In comparison, the designed Ni/TiO2 catalyst calcined at 600 °C (Ni/Ti-600R) with rutile TiO2 as the main component inhibited the formation of the classical SMSI, even after 600 °C H2 reduction, and no excessive TiO2 encapsulated Ni0 particles were observed, so no obvious induction period occurred. This study provides new insights into the relationship of SMSI with crystal phases and the induction period in multiphase catalysis, also a new strategy for designing efficient catalysts.