Vanadium depth profile

UPS studies of supported catalysts are rare. Griinert and coworkers [45] recently explored the feasibility of characterizing polycrystalline oxides by He-II UPS. A nice touch of their work is that they employed the difference in mean free path of photoelectrons in UPS, V 2p XPS and valence band XPS (below 1 nm, around 1.5 nm, and above 2 nm, respectively) to obtain depth profiles of the different states of vanadium ions in reduced V205 particles [45]. However, the vast majority of UPS studies concern single crystals, for probing the band structure and investigating the molecular orbitals of chemisorbed gases. We discuss examples of each of these applications. 

From the theoretical considerations it can be seen that the magnitudes of ki and kj influence the depth at which we can expect to find M-shaped Vanadium deposition profiles in the catalyst bed. The magnitude of the steady state B/A ratio, p, also depends on ki and ka values. If it is assumed that k is proportional to the partial pressure of H- S, the magnitude of k can be changed by changing the partial pressure of H2S. 

---