Desorbability of Chemisorbed Water on Metal Oxide Surfaces. I. Desorption Temperature of Chemisorbed Water on Hematite, Rutile and Zinc Oxide

The desorbability of water molecules chemisorbed on the surfaces of metal oxides has been investigated in the cases of α-Fe2O3, TiO2 (rutile) and ZnO. Water vapor adsorption isotherms were determined on the samples treated at various temperatures in a vacuum of 10−5 Torr. The BET Vm-values of water adsorption were plotted against the temperature of the pretreatment. The curves obtained show a sharp increase at a moderate temperature which is varied by the nature of solid substance. This fact makes us conclude that, at this temperature, the chemisorbed water on oxide surfaces starts to be removed. The variation in the desorption temperature due to the nature of metal oxide is considered to come from the magnitudes of the bonding force of the surface hydroxyl groups to the surface metal atoms on each solid.