Adsorption of water on copper and cuprous oxide

Water adsorption and desorption isotherms are reported for evaporated Cu and Cu2O using a quartz crystal oscillator method with an ultimate sensitivity of 10−8 g cm−2. Cu2O adsorbs more water than Cu at a given relative humidity (RH). Higher adsorbed water content on Cu2O a a given RH partly accounts for the breakdown of its passivity against sulfidation at elevated RH as reported earlier by the author. Isotherms are fitted to a BET‐type (type II) model. From the BET parameters, the monolayer capacity and the heat of adsorption have been computed.