Fine-Tuning of Pt Dispersion on Al 2 O 3 and Understanding the Nature of Active Pt Sites for Efficient CO and NH 3 Oxidation Reactions.

Fine-tuning the dispersion of active metal species on widely used supports is a research hotspot in the catalysis community, which is vital for achieving a balance between the atomic utilization efficiency and the intrinsic activity of active sites. In this work, using bayerite Al(OH) ₃ as support directly or after precalcination at 200 or 550 °C, Pt/Al ₂ O ₃ catalysts with distinct Pt dispersions from single atoms to clusters ( ca . 2 nm) were prepared and evaluated for CO and NH ₃ removal. Richer surface hydroxyl groups on AlO _x (OH) _y support were proved to better facilitate the dispersion of Pt. However, Pt/Al ₂ O ₃ with relatively lower Pt dispersion could exhibit better activity in CO/NH ₃ oxidation reactions. Further reaction mechanism study revealed that the Pt sites on Pt/Al ₂ O ₃ with lower Pt dispersion could be activated to Pt ⁰ species much easier under the CO oxidation condition, on which a higher CO adsorption capacity and more efficient O ₂ activation were achieved simultaneously. Compared to Pt single atoms, PtO _x clusters could also better activate NH ₃ into -NH ₂ and -HNO species. The higher CO adsorption capacity and the more efficient NH ₃ /O ₂ activation ability on Pt/Al ₂ O ₃ with relatively lower Pt dispersion well explained its higher CO/NH ₃ oxidation activity. This study emphasizes the importance of avoiding a singular pursuit of single-atom catalyst synthesis and instead focusing on achieving the most effective Pt species on Al ₂ O ₃ support for targeted reactions. This approach avoids unnecessary limitations and enables a more practical and efficient strategy for Pt catalyst fabrication in emission control applications.