Self-inhibition of water dissociation on magnesium oxide surfaces

Hydroxylated MgO surfaces have been prepared by exposure to water vapour of MgO crystals at room temperature. High hydroxyl coverages were achieved on freshly cleaved surfaces. However, upon adsorption-desorption cycles of th e hydroxyl adlayer, the ability of the MgO surfaces to dissociate water was seen to be dramatically inhibited. Reduced reactivities have also been obs erved on both, air- and water-exposed MgO surfaces. This reactive behaviour is discussed in relation to the theoretical prediction that the MgO(100) f ace is not expected to dissociate water molecules. (C) 1999 Elsevier Scienc e B.V. All rights reserved.