Geometric orientation of the metal atoms in a bimetallic nanoparticle can play a pivotal role in its sensing and activation of different types of molecules. In the present paper, we demonstrate this complex structure-property correlation on model Au-Pt clusters by studying methanol adsorption and oxidation on various conformations of the Au3Pt3 cluster with different relative orientations of the Au and Pt atoms. We have further compared the results with the monometallic Au and Pt clusters. Our results reveal that the adsorption of methanol is least favourable on the monometallic Au 6 cluster as reflected from a very low free energy of complexation (-0.92 Kcal/mol), whereas, the free energy of methanol complexation for the Pt6 is -6.69 Kcal/mol. The bimetallicAu3Pt3 conformers show higher free energies of methanol complexation with notable dependence on the relative orientation of the Au and Pt atoms in the conformer. Likewise, the activation barriers for methanol oxidation are found to be large for the monometallic Au6 cluster as compared to the monometallic Pt6 and bimetallic Au3Pt3 clusters. Further, the activation barriers with respect to O-H and C-H bond activation of methanol are found to be very low and highly sensitive to the relative orientation of the Au and Pt atoms in the bimetallic Au-Pt cluster. Thus, the current study demonstrates that it is possible to tune reactivity and catalytic activity of the cluster by varying its structural features.
Keywords: Bimetalic clusters; geometric orientation, methanol oxidation; density functional theory; O-H and C-H dissociation.