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Free keywords:
Iron oxide, ice, water, adsorption, IRAS, TPD, phase transition, dissociation, atmospheric chemistry
19, Iron oxide model catalysts: adsorption & catalysis
Abstract:
Deuterated water adsorption on epitaxially grown FeO(111), Fe3O4(111) and Fe2O3 (biphase) films was investigated in the range 110 - 320 K by infrared-reflection-absorption-spectroscopy (IRAS) and
temperature programmed desorption (TPD) spectroscopy. At 110K, a first water layer forms on Fe3O4(111) and Fe2O3 (biphase) before the second and higher layers develop. The first half monolayer
on Fe3O4 adsorbs dissociatively. The second half ML develops features characteristic for hydrogen bonding and the formation of dimers is concluded. Also on e2O3(biphase), initial water adsorption is dissociative. A strongly bound minority species is observed. Heating to 169 K causes formation of ice
clusters. On FeO(111) adsorption is molecular and weak. On all studied surfaces, thick ice layers grown at 110 K are amorphous. On Fe3O4(111) they transform at 170 K into hexagonal ice (IceH) while
up to 10 L on FeO(111) remain amorphous. The mechanisms for adsorption and ice formation correlate with structure and termination of the different oxide surfaces
