Redhead analysis

Figure 4.47. Effect of catalyst potential on the desorption activation energy of 02 from Pt/YSZ calculated from the modified Redhead analysis ( ) and from the initial slope of the TPD spectra (O).30 Reprinted with permission from Academic Press.

One can then use the standard Redhead analysis to the data of Fig. 5.24. To this end one uses the Redhead equation in its generalized form derived by Falconer and Madix 48... 

Figure 5.26. Effect of catalyst potential on the oxygen desorption activation energy, Ed, calculated from the modified Redhead analysis for Pt, Ag and Au electrodes deposited on YSZ.44,46 Reprinted from ref. 44 with permission from the Institute for Ionics.

Performing a Redhead analysis of the TPD. an estimation of the activation energy (Ea) of hydrogen desorption from npSi can be derived from the following equation [7], where v is the evolution rate, and p is the linear temperature ramp rate. 

Ed, calculated from the Redhead analysis of O2 TPD spectra for Pt, Ag, and Au electrodes deposited on YSZ. (Reprinted with permission from Ref. 24, Copyright 1997 by Springer). 

Temperature programmed desorption (TPD) is an experimental technique to measure surface kinetic parameters. The most straightforward analysis of TPD is due to Redhead [331], Assuming that the surface has some fractional coverage 0 of adsorbed A molecules, the desorption rate of A from the surface r(j (1/s) is taken to be... 

Despite its wide use, the Redhead model has inherent difficulties such as the heating rate problems mentioned above. An alternative analysis method has been proposed and is outlined below. 

An analysis of the desorption process, using the temperature where the desorption peak is obtained, is given by Redhead [73]. Assuming that v and are independent of the adsorbate concentration a and time t, E es can be obtained for zero-, first-. 

Apart from this approach which implies the evidence of Tmax, there is another which includes the value of peak width in the analysis. Also, many authors rely on the application of other, even more simplified methods that enable the calculation of kinetic parameters. Particularly popular among surface scientists are the Redhead s and Kissinger s methods. 

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