Characterization of Metal-Oxide Catalysts in Operando Conditions by Combining X-ray Absorption and Raman Spectroscopies in the Same Experiment

We have developed a new instrumental setup that combines simultaneous X-ray absorption spectroscopy, Raman spectroscopy and online mass spectrometry for operando studies of catalytic reactions. The importance of combining these techniques in the same experiment is demonstrated with the example of CO oxidation over nanoscale copper oxide catalysts supported on high surface area titanium oxide. X-ray absorption near edge structure (XANES) spectroscopy provides information on the charge state and local geometry of the catalytically active atoms. Extended X-ray absorption fine-structure (EXAFS) technique adds information about their local coordination environment. Raman spectroscopy adds sensitivity to crystallographic phase and long range order that both XANES and EXAFS are lacking. Together, these measurements enable simultaneous studies of the structural and electronic properties of all components present in metal-oxide catalysts. Coupled with online reactant and product analysis, this new setup allows one to elucidate the synergy between different components of a catalytic system and shed light on its catalytic activity and selectivity.