Surface reactions of ethanol on UO${}_2$ thin film. Dehydrogenation and dehydration pathways

The reaction of ethanol has been investigated on a UO${}_2$ thin film by temperature programmed desorption. Two
channels for ethanol desorption are identified. The first, in the 250–500 K region, is coverage dependent while
the second with a maximum peak temperature (T${}_P$) at ca. 630 K is not. The desorption energy, Ed, of the second
channel is found to be equal to ca. 150 kJ/mol with a prefactor of 10${}^{12}$ s${}^{-1}$ and a desorption order n - 2.
This is attributed to surface ethoxides re-combinative desorption. This second desorption channel is accompanied by the
desorption of acetaldehyde (and hydrogen) and ethylene (and water). Acetaldehyde (CH${}_3$CHO) desorption,
produced by the dehydrogenation of ethoxides, was sensitive to surface coverage. Its T${}_P$ changed from 640 K at θ
= 0.06 to 610 K at θ = 1, while ethylene (CH${}_2$––CH${}_2$) desorption Tp, produced by the dehydration of ethoxides
did not shift. The molar ratio of these two products (CH${}_3$CHO/CH${}_2$––CH${}_2$) of 0.8 is similar to that previously
found on a UO${}_2$ (1 1 1) single crystal and fits with the U–O bonding nature that contains a non-negligible fraction
... mehrof covalency.