Ab initio investigation of the role of transition-metal dopants in the adsorption properties of ethylene glycol on doped Pt(100) surfaces

Abstract

Ethylene glycol (EG) has been considered as a promising alcohol for direct alcohol fuel cells, however, our atomistic understanding of its interaction with doped transition-metal (TM) substrates is not well established. Here, we employed density functional theory calculations within the additive van der Waals D3 correction to improve our atomistic understanding of the role of TM dopants on the adsorption properties of EG on undoped and doped Pt(100) surfaces, namely, Pt₈TM₁/Pt₉/Pt(100) and Pt₉/Pt₈TM₁/Pt(100), where substitutional TM dopants (Fe, Co, Ni, Ru, Rh and Pd) are located within the topmost or subsurface Pt(100) layers, respectively. Except for Pd, all the studied TM dopants showed strong energetic preference for the subsurface layer, which can be explained by the segregation energy and charge effects, and it is not affected by the EG adsorption. In the lowest energy configurations of the undoped and doped substrates, EG binds via one OH group, with the anionic O atom located close to the on-top cationic TM site and the H atom parallel to the surface and pointing towards the bridge site. However, at slightly higher energy configurations, EG adsorbs via one OH with the C–C bond almost perpendicular to the surface, or via both OH groups. As expected, the adsorption is stronger on Pt₈TM₁/Pt₉/Pt(100) with EG (OH group) bound to the cationic TM site and a O–TM distance of about 2 Å. Furthermore, doping enhanced the adsorption energy, and hence, decreased the distance between EG and the surface. For all substrates, adsorption induces a reduction of the work function, which is larger for the adsorption of EG via two OH groups.