Adsorption Geometry Determines Catalytic Selectivity in Highly Chemoselective Hydrogenation of Crotonaldehyde on Ag(111)

TPR of Crotonaldehyde and its Hydrogenation Products Figure S1 shows TPR data acquired after adsorption of ~ 1 ML H(a) on progressively increasing amounts of crotonaldehyde (0.3 ML, 0.6 ML, 1 ML in A-C respectively). It is clear that in every case there was a substantial and approximately constant production of crotyl alcohol, with increasing yields of butyraldehyde and, especially, butanol as the initial coverage of crotonaldehyde increased. This decreasing chemoselectivity with increasing crotonaldehyde coverage corresponds to progressive activation of the C=C function towards hydrogenation. The amount of unreacted crotonaldehyde desorbing from the surface also increases with increasing crotonaldehyde coverage as overall conversion decreases. The small amounts of butyraldehyde and butanol desorbing at ~ 230 K and ~ 300 K, respectively, are possibly due to hydrogenation occurring at defect sites.