A comparison of the dominant pathways for the methanol dehydrogenation to CO on Pt7 and Pt7−xNix (x = 1, 2, 3) bimetallic clusters: A DFT study

Density functional theory based calculations have been employed to investigate structures and properties of coupled tetragonal pyramid (CTP) Pt7 based Pt(7−x)Nix (x = 1, 2, 3) bimetallic clusters, and the reaction mechanism of methanol dehydrogenation to CO on Pt7 and PtNi bimetallic clusters. The models chosen to catalyze the methanol are Pt7 (CTP, quintet) cluster and Pt5Ni2 (I) cluster (two Pt atoms in the bottom of Pt7 (CTP) are replaced by Ni atoms) which is the most stable structure among all the isomers of Pt(7−x)Nix (x = 1, 2, 3). The methanol dehydrogenation on Pt7 (CTP) cluster preferentially proceeds along the pathway of CH3OH → CH2OH → CH2O → CHO → CO, while on Pt5Ni2 (І) the pathway of CH3OH → CH3O → CH2O → CHO → CO is more favorable. In addition, the complete dehydrogenation product of methanol, CO, can more easily dissociate from Pt5Ni2 (I) than that on Pt7. Electronic configuration analysis shows that charge transfer from Ni to Pt and results in increase of the electron density in Pt 5d orbitals. Moreover, the density of states (DOS) at Fermi level of clusters reduces gradually as the increase of the doped Ni atoms and this improves the catalytic activity for methanol decomposition.