Mechanistic Insight into the Facet-Dependent Adsorption of Methanol on a Pt₃Ni Nanocatalyst

There is great interest in the design of catalysts for use in direct methanol fuel cells (DMFCs). However, our atomistic understanding of the adsorption and oxidation mechanism of CH₃OH at the different crystal planes of metal catalysts is far from satisfactory. This study endeavors to gain mechanistic insight into the intrinsic facet-dependent adsorption properties of CH₃OH on the surface of a Pt₃Ni catalyst. We analyzed the adsorption characteristics of CH₃OH by optimizing the structures and calculating the adsorption energies at each site on the (111), (100), and (110) surfaces of a Pt₃Ni catalyst using density functional theory (DFT) calculations with van der Waals (vdW) corrections to the total energy. Our results indicate that the adsorption strength of CH₃OH at the surface of the Pt₃Ni catalyst is facet-dependent, following the order (110) > (111) > (100). The mechanism of the facet-dependent adsorption of CH₃OH on the catalyst is rationalized in terms of shifts of the <i>d</i>-band center of the Ni component relative to the Fermi level, density of states, changes to the work function of each surface of the Pt₃Ni catalyst, and polarization effects of the adsorbed CH₃OH. We believe that the present results will provide useful information to help guide the rational design and construction of nanoarchitectured catalyst surfaces for optimal heterogeneous catalysis