Time‐resolved DRIFT Spectroscopy Study of Carbonaceous Intermediates during the Water Gas Shift Reaction over Au/Ceria Catalyst
Julia Vecchietti, Gustavo Belletti, Paola Quaino, Adrián L. Bonivardi, Sebastián E. Collins
Abstract
Abstract ChemCatChem homepage for more articles in the collection. The mechanism of the low‐temperature water gas shift reaction (LTWGS) on an Au/CeO 2 catalyst was investigated by means of in situ diffuse reflectance infrared (DRIFT) spectroscopy. Under steady‐state LTWGS reaction (373–623 K), the catalyst is partially reduced, and signals from carbonate/formate dominates the infrared spectra. Time‐resolved pulse of CO experiment under a constant partial pressure of water at 423 K indicates that Ce 4+ can be reduced to Ce 3+ and that formate (HCOO) species cannot be directly related to the CO 2 production. Further information was obtained by performing modulation excitation spectroscopy (MES) experiments coupled with a phase‐sensitive detection (PSD) method. Under periodic modulation of the CO partial pressure while keeping the H 2 O concentration constant, most of the intense bands of carbonate and formate remained constant, indicating that these species are only spectators. The same is observed for the concentration of Ce 3+ . Conversely, signals in‐phase with the conversion of CO to CO 2 are observed and assigned to carboxyl [C(O)OH] and carboxylate (CO 2 δ− ) species, while some monodentate formate (m‐HCOO) also changes but at a lower rate. A plausible associative reaction mechanism where carboxyl/carboxylate are key intermediates is postulated.