Effects of crystal structure of TiO2 on Pd-based catalysts†

Abstract

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.