April 16, 2018

How strain can break the scaling relations of catalysis

Eigenstress is a simple guideline for strain effects.

Catalysts alter chemical pathways by binding to reaction intermediates. It is well-known that straining the catalyst can directly affect how strongly these adsorbates bind to the surface. In a work published in Nature Catalysis, we provide a framework for understanding these effects in catalysis based on the mechanical concept of eigenstress.

Put simply, when an adsorbate binds to a surface, it creates a force on the neighboring atoms: this force can either act to push the neighbors away or pull them in, as shown in the figure. If the adsorbate pushes the neighbors away (called positive eigenstress), putting the material under a positive strain will act to relieve these forces, and thus strengthen the interaction. Conversely, negative strain will work against these forces and destabilize the interaction, leading to weaker binding. The oppositive is true if the adsorbate creates a negative eigenstress.

For catalysis, this provides a framework by which we can tailor the binding strength of reactive intermediates independently, which can be accomplished simply by applying anisotropic strain. This can break the scaling relations between adsorbates, which otherwise constrain the tunability of catalysts.

You can read about the research here or find the complete article in Nature Catalysis.