Adsorption on tungsten

There is further emphasis on adsorption isotherms, the nature of the adsorption process, with measurements of heats of adsorption providing evidence for different adsorption processes - physical adsorption and activated adsorption -and surface mobility. We see the emergence of physics-based experimental methods for the study of adsorption, with Becker at Bell Telephone Laboratories applying thermionic emission methods and work function changes for alkali metal adsorption on tungsten. 

Equation (89) shows that the allowance for the variation of the charge of the adsorbed atom in the activation-deactivation process in the Anderson model leads to the appearance of a new parameter 2EJ U in the theory. If U — 2Er, the dependence of amn on AFnm becomes very weak as compared to that for the basic model [see Eq. (79)]. In the first papers on chemisorption theory, a U value of 13eV was usually accepted for the process of hydrogen adsorption on tungsten. However, a more refined theory gave values of 6 eV.57 For the adsorption of hydrogen from solution we may expect even smaller values for this quantity due to screening by the dielectric medium. 

A paper by 0. Beeck (33d) has only recently come to the author s notice. Working with evaporated films of metal of area of the order of 10,000 cm. Beeck has confirmed all Roberts results on the speed, extent, and heat of adsorption as a function of surface covered, for the adsorption of hydrogen on tungsten. Nickel shows a similar behavior. This makes extremely likely the view that adsorption on tungsten powder is complicated in some fashion, if not by solution, as suggested above, then by some kind of physical or chemical heterogeneity of the surface, as in the Halsey and Taylor picture. 

Figure 3.6 Frexmdlich interpretation of H2 adsorption on tungsten powder. [Reprinted with permission from W.G. Frakennberg, J. Amer. Chem. Soc., 66, 1827, copyright by the American Chemical Society, (1944).]...

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