<i>Operando</i> Polarization-dependent Total Reflection Fluorescence (PTRF) XAFS Measurements of Three-dimensional Structures of Catalytic Active Sites

A novel operando X-ray absorption fine structure (XAFS) technique was developed that we have called the operando polarization-dependent total reflection fluorescence (PTRF)-XAFS technique, which can provide information on the electronic state and three-dimensional (3D) structure of active metal species dispersed on a well-defined single-crystal surface during catalytic reactions. This technique was applied to the Pt/α-Al2O3(0001) surface during CO oxidation, and precise relationship between the 3D structure and catalytic activity of active Pt sites was evaluated.