Opportunities for Tuning Surface Reactivity

Given a certain metal, what can we do to alter its reactivity First there is the structure of the surface. More open surfaces expose atoms of lower coordination. This narrows the d band, and shifts its position (up if it is more than half filled, down if the d band is less than half filled). To illustrate the point Tab. 6.2 shows experimentally determined activation energies of NO dissociation on the (111) and (100) surfaces of rhodium. 

Methane is a stable molecule and therefore hard to activate. As a result the sticking probability for dissociative chemisorption is small, of the order of 10 only, and ruthenium is more reactive than nickel. However, a stretched overlayer of nickel is significantly more active than nickel in its common form, in agreement with expectation. 

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