Reactivity of CO on bimetallic Ni3M clusters (M=Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Rh, Ru, Ag, Pd and Pt) by Density Functional Theory

This work introduces adsorption and dissociation of CO on doped Ni3M clusters, where M=Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Rh, Ru, Ag, Pd and Pt, applying density functional theory for the search of best catalyst for CO dissociation. The butterfly geometry is observed for Ni3Sc, Ni3Ti and Ni3Cr and other clusters are remain distorted tetrahedral geometry. Presence of the odd number of valence electrons, for example in Ni3Sc, Ni3V, Ni3Mn, Ni3Co, Ni3Cu, Ni3Rh and Ni3Ag clusters are open shell structure showing greater stability than the closed shell clusters. But, the higher stability of closed shell Ni3Ti cluster is due to the presence of more number of polar M-M bonds. Adsorption of CO on all the doped clusters are thermodynamically feasible. Dissociation is not thermodynamically feasible for all the clusters except on Ni3Sc. Though doping of all the metals in Ni4 cluster decreases CO dissociation barrier, all the bimetallic clusters are not good catalyst for CO dissociation. The formation of TiO, VO, CoO and MnO species can reduce the catalytic activity of the doped Ni4 cluster. Surface C binds at three fold sites for most of the cluster. But for Ni3Fe cluster C is tetra coordinated strongly binds Fe forming a σ and a π bond. Surface O in Ni3Cu binds at three fold site having unpaired electrons, more nucleophilic than surface O of Ni3Fe cluster. Higher positive ΔG values and lower stability of the doped clusters and adsorption system can reduce the efficiency of the catalyst. Thus, Ni3Fe and Ni3Cu might be the best catalysts for CO dissociation.