Controlling the Strong Metal-Support Interaction Overlayer Structure in Pt/TiO 2 Catalysts Prevents Particle Evaporation.

Platinum nanoparticles (NPs) supported by titania exhibit a strong metal-support interaction (SMSI) [1] that can induce overlayer formation and encapsulation of the NP's with a thin layer of support material. This encapsulation modifies the catalyst's properties, such as increasing its chemoselectivity [2] and stabilizing it against sintering. [3] Encapsulation is typically induced during high-temperature reductive activation and can be reversed through oxidative treatments. [1] However, recent findings indicate that the overlayer can be stable in oxygen. [4, 5] Using in situ transmission electron microscopy, we investigated how the overlayer changes with varying conditions. We found that exposure to oxygen below 400 °C caused disorder and removal of the overlayer upon subsequent hydrogen treatment. In contrast, elevating the temperature to 900 °C while maintaining the oxygen atmosphere preserved the overlayer, preventing platinum evaporation when exposed to oxygen. Our findings demonstrate how different treatments can influence the stability of nanoparticles with or without titania overlayers. expanding the concept of SMSI and enabling noble metal catalysts to operate in harsh environments without evaporation associated losses during burn-off cycling.