Pt catalysts are known to sinter and form abnormally large particles during high temperature aging in air1. The role of the support and additives is not well understood. We have developed a novel approach to provide insights into the phenomena during the evolution of particle size during catalyst sintering. The model catalysts2 allow us to treat samples at high temperatures for short times (seconds) so that we can quantify the rates of emission and capture from individual nanoparticles. We have studied the evolution of Pt catalysts heated in air, where volatile oxides of Pt enhance the rates of catalyst sintering. PdO can effectively trap mobile Pt species forming bimetallic Pt-Pd nanoparticles3. Pd helps slow the rates of vapor phase processes, but has only limited impact on the surface mediated growth of particles. In contrast Pt actually speeds up the sintering of Pd, which otherwise is quite stable in oxidizing conditions. The model catalyst approach provides unique insights into the trapping of mobile species, nucleation, growth and regeneration of nanoparticles in heterogeneous catalysts. 1 Johns, T. et al., ChemCatChem, 5 (2013) 2636. 2 Moodley et al., Catalysis Today, 154 (2010) 142. 3 Carrillo et al., J. Phys. Chem. Lett., 5 (2014) 2089.

Insights into emission and capture of atoms during Ostwald ripening

249th National Meeting (2015)

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