Because of its relative simplicity, the WGS reaction is an ideal system for studying catalytic chemistry on supported noble metal surfaces at the molecular level. Evidence suggests that WGS catalysts operate in a bi-functional manner with contributions from both the dispersed metal as well as the support in activating CO and H2O, respectively1,2. For this work, operando infrared spectroscopy (IR) and isotopic transient experiments are combined in order to examine the working state of Pt/Al2O3, Na-Pt/Al2O3, Na-Pt/TiO2, Pt/CeO2, and Pt/ZrO2 under reaction conditions and to correlate catalyst performance with surface features related to CO and H2O activation. CO/13CO and H2O/D2O isotope switches are used to quantify the surface coverages of carbon-containing (NC) and deuterium-containing (ND) active intermediates, respectively. Kinetic measurements, which show a normal H/D kinetic isotope effect (KIE) ranging from 2.2 on Pt/Al2O3 to 2.6 on Pt/CeO2, along with the time-resolved IR spectra of transient surface species, reveal that O-H bond breaking is involved in the rate-determining step for the Pt catalysts examined in this study. The implications of these findings on the elementary kinetic steps for WGS, the nature of the catalytic sites, and the variation in WGS TOR on supported Pt catalysts will be discussed. References (1) Kalamaras, C. M.; Panagiotopoulou, P.; Kondarides, D. I.; Efstathiou, A. M. Journal of Catalysis 2009, 264, 117. (2) Jacobs, G.; Patterson, P. M.; Graham, U. M.; Sparks, D. E.; Davis, B. H. Applied Catalysis A: General 2004, 269, 63.

Water activation by the supports for Pt catalysts during the water-gas shift reaction

251st National Meeting (2016)

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