Transient Analysis and Promotion Index

As previously noted, determination of the promotion index PI0s- of the promoting oxide ions O6 requires knowledge of the coverage of O6 on the 

Consequently c can be obtained from the initial slope of ln(r/ro) vs t. For the rate transient upon current imposition (Fig. 5.6b) one can estimate a c value of 6.5. 

Once c has been estimated, one can then compute 0o fom Eq. (5.9) for any time t from the corresponding r/r0 value, i.e.  

The maximum 0os value is thus computed for the transient of Fig. 5.6b to be 0os 0.5. This, in view of the definition of the promotion index, PI, (Chapter 4) and the observed p value (p 16.5) gives a PIQ5- value of the order of 30, in good qualitative agreement with PI0s- values for other Pt catalyzed oxidations.5 

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