New Trends in Chemistry at Steps Due to Mechanical Stress and Relevance to Design of Catalytic Interfaces

The control and optimization of catalytic processes is a key goal in many technologies.  Here, we demonstrate via computation that the application of mechanical stress to late transition metals (LTM) can modify chemisorption energies at stepped surfaces, and thus catalytic activity, in ways not previously envisioned.  Specifically, compressive stresses can induce stronger binding of chemical species at steps on LTM surfaces, which is the opposite of the well-established trend found on LTM close-packed surfaces.  The mechanism driving this new stress effect is shown to be the mechanical relaxation of the deformed metal during chemisorption, which can be larger, and of the opposite sign, than the electronic effects due to changes in the d-band structure; i.e. the trends predicted by the widely-held “d-band” model are violated.  Application of stress can thus simultaneously shift binding energies on steps up (or down) and on terraces down (or up) on the same LTM surface, and potentially increase overall catalytic activity in wide classes of systems.