Nonstoichiometric catalyst compositions

Figure 2. These high-resolution micrographs show how a so-called x-ray amorphous, nonstoichiometric molybdenum sulfide catalyst exhibits structural (as well as compositional) heterogeneity. Amorphous, quasi-crystalline, and crystalline regions coexist at the ultramicro level (18,).

The other catalyst supports as a nonstoichiometric mixture of several titanium oxide phases that have hypo-d-electron character have an ability to interact with inert noble metals, like platinum, changing additionally the catalytic activity of the platinum as catalyst. However, very low specific surface area (the maximum value referred is 15 m g ) prevents high dispersion and good compositional homogeneity of the catalyst clusters which is an important request for the activity of the catalyst. 

Tungsten-based materials as n-type semiconductor with nonstoichiometric compositions are extremely stable under electrochemical oxidation conditions and could be used as a non-carbon support for catalyst. The interest in their use as catalyst support is due to the possible synergetic effect between metal catalyst and support. 

---