Characterizing catalyst stability by identifying the predominant mechanisms, timescales and driving forces of catalyst reconstruction under relevant reaction conditions is necessary for the design and commercialization of new catalysts. Here, we study Rh/TiO2 catalysts under CO2 hydrogenation conditions (573-873 K and feed of 75% H2, 25% CO2 at 1 atm) at high conversion and utilize reactivity studies along with ex-situ and in-situ spectroscopy and microscopy to characterize changes in catalyst activity and structure as a function of time on stream and the initial catalyst structure. We find that the catalysts reconstruct through various mechanisms including Rh particle fragmentation to form single Rh atoms, TiO2 encapsulation of Rh particles, single Rh atom sintering via Ostwald Ripening and Rh nanoparticle sintering via migration and coalescence. The relative influence of these reconstructions on catalytic reactivity is a complex function of initial Rh weight loading, operating temperature, overall catalyst loading, etc. In this talk, I will discuss both mechanistic studies examining the evolution in catalyst structure and function for this system and initial efforts to develop machine learned models that predict this behavior.
