Adsorption of hydrogen on evaporated cobalt films

Hydrogen adsorption on evaporated Co films has been studied by means of measurements of the surface potential changes that occur during this process, and analysis of the desorption spectrum of hydrogen. It has been observed that hydrogen adsorbed at 78 K on Co films exists in three forms with essentially different electrical properties: atomic, electronegatively polarized β^? form; atomic, electropositively polarized β⁺ form and reversibly adsorbed, molecular, positively polarized α form. The β^? form is not homogeneous from the point of view of the bond energy with the metal surface and consists of the states β_s^? and β^? characterized by activation energy of desorption 10.0 and 18.8 kcal/mol H₂ correspondingly. The Activation energy of desorption of the β⁺ form is low, i.e. 2.1 $\text{kcal}\text{mol}$ H₂.