The adsorption of carbon monoxide on evaporated metal films

Abstract

Calorimetric measurements at room temperature have been made of the heats of adsorption of carbon dioxide on evaporated films of iron, cobalt, nickel, titanium, molybdenum, tungsten, tantalum and niobium. These new data, considered along with similar data obtained previously for oxygen and carbon monoxide, provide strong evidence for dissociative adsorption of carbon dioxide into CO and O, except possibly on iron, cobalt and nickel. The saturation coverages for the adsorption of carbon dioxide on all the metals are distinguished by their smallness. Despite this, the adsorptive capacity for hydrogen of surfaces saturated with carbon dioxide is very small, except for nickel and to a lesser degree for iron. These observations have also been accounted for in terms of dissociative adsorption of carbon dioxide and the concentrations of krypton atoms in the monolayer deduced previously. For nickel and cobalt (and to some extent iron), adsorption of carbon dioxide in an undissociated form is a distinct possibility, but a clear conclusion cannot be reached. The linear dependence of heat of adsorption on metallic radius is discussed.