Modification of dehydrogenation activity of nickel on O-covered Mo(1 1 0)

The reactivity of methanol on Ni (θ⩽1.2 ML) on Mo(1 1 0)–(1 × 6)-O is studied using temperature programmed reaction and X-ray photoelectron spectroscopies. Carbon monoxide, D2O, D2, and formaldehyde are evolved from CD3OD. The formaldehyde production represents a departure from reactivity typical for nickel, which usually promotes complete dehydrogenation. Similarly, formaldehyde production is atypical of Mo(1 1 0)–(1 × 6)-O. Isotopic labeling studies using CH3OH, CD3OD, CD2HOH and Mo(1 1 0)–(1 × 6)-18O show that formaldehyde is produced from irreversible C–H(D) bond dissociation of methoxy. Furthermore, there is a significant kinetic isotope effect in production of formaldehyde, such that yields from the CH3OH reaction are ∼4 times less than formaldehyde yields from the CD3OD reaction. Differences in the satellite structure of the Ni(2p) peaks for Ni deposited on Mo(1 1 0)–(1 × 6)-O compared to Ni on clean Mo(1 1 0) provide evidence for subtle perturbations of the electronic structure of the Ni deposited on the oxygen overlayer, possibly associated with formation of a strained Ni layer. X-ray photoelectron data also rule out the possibility that the difference in reactivity for Ni deposited on clean vs. the (1 × 6)-O overlayer is due to oxygen migration from the Mo to the Ni. Finally, the variation in formaldehyde yields as a function of Ni coverage is used to rule out special edge or defect sites as the reaction centers leading to formaldehyde production. These results suggest that interfacial interactions can be used to modify the electronic structure of metals so as to alter reaction selectivity.