Infrared Absorption of Zinc Oxide and of Adsorbed CO2. II

Abstract
Reversible changes due to gas adsorption in spectra of powdered zinc oxide were observed. In the range 2000∼1200 cm—1, CO2 gave increases in absorption at 1640 and 1430 cm—1 on adsorption at 20°C and at 1570 and 1380 cm—1 at 200°C. These results could be interpreted by assuming that CO2 adsorbed at 20°C is combined with surface oxygen, but that at 200°C bonded to surface zinc. Another change, a decrease in the conduction‐electron absorption of the solid, was found in the case of adsorption at 200°C. Similar decreases by adsorption of O2, C2H4, and H2 (of opposite sign) are reported. Correlation between the adsorbed state of CO2 and influences of the adsorption on electrons in the solid is discussed. Some data on adsorption velocities and adsorbed quantities of CO2 are given.