The recombination of oxygen atoms at salt and oxide surfaces

Abstract

The efficiencies with which surfaces of potassium chloride, lithium chloride, lead monoxide and molybdenum trioxide cause the removal of oxygen atoms produced in the gas phase by an electrodeless discharge have been determined. It has been shown that the process occurring at potassium and lithium chloride surfaces is first order. Their activity at room temperature is about the same as that of glass, but, with both, it increases approximately one hundred fold as the temperature is raised to 400° C. Both surfaces show hysteresis on cooling, and it is probable that this is related to the loss and subsequent recovery of water by the surface. Molybdenum and lead oxide are much more active at room temperature than glass, the activity of the latter increasing with rise of temperature. The effect of temperature on the activity of a molybdenum oxide surface is uncertain. The mechanism of oxygen atom removal at both glass and the above surfaces has been discussed. It is concluded that, with glass and the oxides, the most probable mechanism is that oxygen atoms from the gas phase react with combined oxygen atoms in the surface, and that the defects so caused are eliminated rapidly from the gas phase.