Effects of crystal structure of TiO2 on Pd-based catalysts

It is generally acknowledged that the crystal structure of the support plays a crucial role in the catalytic performance, however, the exact role of crystal structure in the catalytic system remains controversial. The Pd/TiO2 catalysts designed in this study with different crystals (rutile (r) and anatase (a)) were employed to study the effects of the crystal structure via a probe reaction for oxygen removal under a hydrogen atmosphere. Under the same reaction conditions, the temperature to achieve 90% O2 conversion on Pd/a-TiO2 could reach up to 150 °C, which is ∼1.4 times (107 °C) that of the Pd/r-TiO2 catalyst. Based on the various characterization results, it is found that strong metal support interactions (SMSIs) are dominant on the Pd/r-TiO2 catalyst, which could facilitate the formation of oxygen vacancies and Pd2+ species in the active sites, resulting in excellent catalytic performance. This study not only improves the understanding of the distinctive structural properties of TiO2 crystal support but also offers an effective strategy to design efficient heterogeneous catalysts via tuning SMSIs.