Chemistry of Methanol and Ethanol on Ozone-Prepared α-Fe₂O₃(0001)

The preparation of α-Fe₂O₃(0001) single-crystal surface by argon ion sputtering followed by ozone annealing is demonstrated to achieve a stoichiometric surface termination not attainable with molecular oxygen. Both methanol and ethanol thermally react on the stoichiometric α-Fe₂O₃(0001), and three different desorption states were found. At temperatures above 600 K a dehydrogenative disproportionation pathway to yield the respective aldehyde was found, while two peaks at lower temperatures were observed. The peak at 380 K is assigned as dissociative adsorption and recombination, while the less strongly bound peak at 285 K is attributed to molecular adsorption. The mechanism is attributed to a dissociative adsorption mediated by extra atomic oxygen species on top of iron surface sites from the ozone preparation. The absence of photochemical reaction for neither methanol nor ethanol shows that no hole-driven chemistry occurs on stoichiometric α-Fe₂O₃(0001).