Carbon monoxide desorption, spectra

Adsorbed carbon monoxide on platinum formed at 455 mV in H2S04 presents a thermal desorption spectrum as shown in Fig. 2.4b. As in the case of CO adsorption from the gas phase, the desorption curve for m/e = 28 exhibits two peaks, one near 450 K for the weakly adsorbed CO and the other at 530 K for the strongly adsorbed CO species. The H2 signal remains at the ground level. A slight increase in C02 concentration compared to the blank is observed, which could be due to a surface reaction with ions of the electrolyte. Small amounts of S02 (m/e = 64) are also observed. 

Thermal desorption spectroscopy provides information about the heat of adsorption of atoms and molecules at solid surfaces [13]. When heating the solid at a well defined rate (in the range of 4-20°/sec), there is a specific temperature at which the desorption rate is a maximum and from which the heat of desorption can be obtained. When the thermal desorption spectrum is taken at different surface coverages, as shown for carbon monoxide in figure 15, one observes a shift in the peak desorption temperature indicating a variation in the heat of adsorption with coverage. 

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