Atomic Iodine Desorption from Single Crystal Nickel Surfaces
| Autor: | Vicki H. Grassian, K. B. Myli |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Langmuir. 11:849-852 |
| ISSN: | 1520-5827 0743-7463 |
| Popis: | Atomic iodine desorption from single crystal nickel surfaces, Ni(100) and Ni(111), has been monitored by temperature-programmed desorption (TPD). CF 3 I was used as a precursor molecule for iodine adsorption. At low coverages, θ iodine = 0.016 ML, the temperature of the desorption rate maximum (T max ) is near 1035 K for desorption from Ni(100) whereas at higher coverages, θ iodine = 0.20 ML, the temperature decreases to 970 K. There is a similar decrease in T max with increasing coverage for iodine desorption from Ni(111). Analysis ofthe TPD data shows that iodine desorption follows first-order reaction kinetics with a coverage-dependent activation energy. We have modeled the coverage-dependent activation energy of desorption, E des (θ), in terms of a repulsive dipole-dipole interaction, E dip (θ), in the adsorbed layer, where E des (θ) = E des (θ = θ) - E dip (θ). The activation energy of desorption at low coverages, E des (θ = 0), was determined to be 249 and 214 kJ/mol from Ni(100) and Ni(111), respectively. The activation energy decreases by approximately 7% in the coverage range studied, θ = 0 - 0.20 ML. Simulated desorption curves agree well with the experimental data. |
| Databáze: | OpenAIRE |
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