In situ GISAXS-GIWAXS study of the sintering of model Pt-based nanocatalysts during redox cycling

Metal nanoparticle (NP) catalysts promote a broad set of chemical reactions. However, in most hydrocarbon transformation processes, severe deactivation occurs by (i) coke-poisoning of the active metal NP surface in (reductive) CxHy streams and (ii) NP sintering during subsequent O2-based coke burn-off, i.e. (oxidative) regeneration. Yet, the impact of the extent of coke deposition on NP sintering during reaction-regeneration cycling has not been interrogated systematically. Here, ALD-tailored model Pt NP catalysts with pre-selected NP size and spacings will be used to perform controlled reaction-regeneration cycling experiments using reductive gas streams which produce variable extents of coking: C3H8 > C3H8-H2 > H2. In addition, the stabilizing effect of an ultrathin MgO coating on the low coordination Pt sites will be investigated. By applying in-situ GISAXS-GIWAXS during the reaction-regeneration experiments, the NP size and spacing will be monitored in real-time (GISAXS), and the sintering/diffusion dynamics probed with single NP sensitivity (GIWAXS). The proposed investigation might have widespread implications in our understanding of the impact of coke deposition on NP sintering rates and provide guidelines for coke-management and NP stabilization.