Interaction of biogenic impurities with the Ni(111) catalyst surface was studied to understand the important role played by them in inhibiting catalysis. Non-bonding interactions of amino acids (Alanine (Ala), Cysteine (Cys), Methionine (Met), Tryptophan (Trp), Histidine (His), Lysine(Lys), Glutamic acid (Glu) and Threonine (Thr)) in aqueous enivronment were examined using classical molecular dynamics (MD) simulations. The potential of mean force (PMF) profiles of amino acids revealed qualitative differences, resulting into altered orientation and preferential interacting site with the metal surface. Most of the preferential interacting sites were observed to be in direct contact with the<br/>surface except Lys which interacted with the backbone nitrogen oriented away from the surface. The strength of nonbonded interactions varied from -13 to -71 kJ/mol with Ala as the weakest and Trp as the strongest adsorber. The interaction energies scaled linearly with the solvent accessible surface area of the amino acids. DFT calculations showed strong binding for both Cys (-123 kJ/mol) and Met (-102 kJ/mol), undergoing dissociation to form atomic S with an intrinsic activation barrier of 133 kJ/mol and 60 kJ/mol respectively for the C-S bond cleavage on the Ni (111) surface. However, the mechanistic routes for dissociation followed by the two amino acids were a bit different. The mechanistic insights thus obtained lead to an explorative theoretical framework for the design of a bimetallic catalyst which may be used in such an integrated bio and chemo-catalytic process with reduced chances of deactivation. The NiAu alloy surface was calculated to show both reduced Met (-88 kJ/mol) and S binding (132 kJ/mol), as compared to pure Ni surface, indicating promising prospects for the activity of such an alloy catalyst.

Understanding heterogeneous catalyst deactivation by biogenic impurities on Ni (111) surface and bimetallic alloy

254th National Meeting (2017)

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