WATER-ADSORPTION AND THERMAL-DECOMPOSITION ON FEAL(110)

H2O chemistry on FeAl(110) has been investigated with temperature-prog rammed desorption (TPD), photoelectron spectroscopy, and high-resoluti on electron energy loss spectroscopy (EELS). Exposure of FeAl(110) to water at 123 K results in predominantly dissociative adsorption (i.e., H2O --> OH(ad) + H-(ad)), although molecularly adsorbed H2O is also d etected. All, or at least the majority, of the adsorbed H2O converts t o adsorbed OH(ad) by 173 K. Photoemission suggests that the atomic com position of the OH(ad) binding site is primarily Al. Substantial decom position of the OH(ad) adlayer occurs by 300 K, and the majority of th is species dissociates by 410 K. Atomic oxygen resulting from OH decom position (i.e., OH(ad) --> O-(ad) + H-(ad)) remains on the surface as aluminum oxide, and surface hydrogen combines and desorbs as H-2 in th e 200-400 K temperature range. This later reaction step is thought to be strongly influenced by the Fe component of the alloy.