EXAFS, viii

The composition and chemical state of the surface atoms or molecules are very important, especially in the field of heterogeneous catalysis, where mixed-surface compositions are common. This aspect is discussed in more detail in Chapter XVIII (but again see Refs. 55, 56). Since transition metals are widely used in catalysis, the determination of the valence state of surface atoms is important, such as by ESCA, EXAFS, or XPS (see Chapter VIII and note Refs. 59, 60). 

However, EXAFS data show that in reality the average Pd particle size is larger in Pd/NaY than in Pd/HY. This observation is clearly related to the interaction of small Pd particles with zeolite protons, which will further be discussed in Section VIII. A change of Pt particle morphology in zeolite L has also been reported due to H2 (26). This effect has tentatively been attributed to the support, though its chemical nature remains to be clarified. 

PLATE VIII Top left - framework structure of ETS-IO right - local structure around framework Ti in ETS-10, as determined from EXAFS and computer modelling bottom left - comparison between experimental and simulated EXAFS data for ETS-10. 

---