(582h) Understanding Heterogeneous Catalyst Deactivation By Biogenic Impurities on Ni (111) Surface and Bimetallic Alloy

Authors: 
Gupta, M., Indian Institute of Technology Delhi
Khan, T. S., Indian Institute of Technology Delhi
Gupta, S., Indian Institute of Technology Delhi
Alam, M. I., Indian Institute of Technology Delhi
Agarwal, M., Indian Institute of Technology
Haider, M. A., Indian Institute of Technology, Delhi
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
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.