The infrared spectrum of hydrogen chemisorbed on zinc oxide

Chemisorption of hydrogen on pure zinc oxide at 30 °C produces bands at 2.86 and 5.85 μ which are attributed to oxygen-hydrogen and zinc-hydrogen stretching vibrations. The ratio of the intensities of these bands remains constant as the intensities of both bands increase with increasing hydrogen pressure up to 4 cm. Above a pressure of 4 cm, an excess of loosely bonded OH is observed. In addition to the covalent chemisorption which produces OH and ZnH bands, there is a slow chemisorption at 30° which does not produce detectable infrared bands. This slow chemisorption is attributed to H+. When the zinc oxide is heated above 80 ° in hydrogen at constant pressure both bands decrease while again maintaining a constant ratio between OH and ZnH intensities. Above 80 ° an increase in the electrical conductivity is indicated by a decrease in the background transmission. It is concluded that the irreversible change in conductivity is due to reduction of the zinc oxide. It is also concluded that the high temperature maximum which is commonly observed for hydrogen-zinc oxide isobars is not due to formation of an OH species.