Catalysts are the workhorses of the chemical industry, and play an essential role in energy conversion processes and pollution abatement. Novel catalysts and processes must be developed to make our society sustainable. Such development is greatly helped by the understanding of how the catalyst functions. The achievement of such relationship is the main aim of our research. In situ and operando characterization is essential to capture the structure of active sites, however, performing an operando experiment is no guarantee that the active species are actually revealed. Catalysts often consist of nano-sized catalyst particles on a support. It has been recognized since long that the role of the support is not only to stabilize the catalytically active particles of particular size, shape and composition, but that they may actively participate in the catalytic reaction. Specific reaction steps may occur completely on the support or at the metal-support interface. Ceria is an often-used catalyst support and catalytic material because of its ability to reversibly store oxygen. Thus, in oxidation reactions, oxygen activation may occur on ceria and the reaction at the interface of metal and support. The role of Ce3+ is often invoked to explain catalytic activity; however, a quantitative understanding of its role is lacking. Using transient X-ray emission and absorption spectroscopy, we were able to distinguish between Ce3+ that participates in a catalytic cycle, oxidation of carbon monoxide over Pt/CeO2, and Ce3+ that does not contribute to catalytic conversion and is thus a spectator. The reaction takes place at the metal-support interface and the rate of reaction correlates to the rate of ceria reduction, not the oxygen storage capacity.

About in situ and operando characterization of catalysts

2019 Fall National Meeting

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