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

Abstract

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 d-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.