A DFT Study of the Adsorption and Dehydrogenation of Ethanol on a Pt3Sn1 Catalytic Surface
Authors: Ribadeneira Paz Rafael 
Published: February 2020

The selective conversion of oxygenated hydrocarbons is important for several chemical processes as the production of propylene glycol from lactic acid, oxidation of alcohols in fuel cells, hydrogen production. Particularly searching for alternative energy converters, the selective conversion of oxygenated hydrocarbons is the great interest for the development of the Direct Ethanol Fuel Cells (DEFCs). These devices are an interesting solution for the environmental pollution and sustainable development [1-4].

The oxidation reaction mechanism (ORM) on the anodic catalyst in the fuel cell is very important for the development of DEFCs. In the literature are proposed several reaction mechanisms on different catalytic surfaces based on the mixture Pt-M, the problem in these proposed reaction mechanisms is that the whole identification of all the intermediates on each specific Pt based catalyst and the reaction paths involved in the complex process of the ethanol reaction on a catalytic surface is really difficult [5-8]. Currently the main steps identified in different investigations in several Pt based catalysts are in general: the ethanol adsorption, the alcohol decomposition, carbon monoxide (CO) adsorption (catalyst poisoning), the complete oxidation of the CO toward CO2 and the formation of different intermediates (acetaldehyde, acetic acid, water and others) [9-14].

To contribute to clarify the problem of selectivity in catalysts for DEFCs, the potential energy surface (PES) of the adsorption and dehydrogenation steps of the ethanol decomposition on a specific catalytic surface Pt3Sn1 is investigated in this work, using self-consistent periodic slab calculations based on density functional theory (DFT). This research reveals that ethanol does not have a unique mode of adsorption on this catalytic surface, as well as the dehydrogenation pathway does not only proceed via the ethoxy species formation, but also via the 2-hydroxyethyl species formation. Additionally it is showed that acetaldehyde desorbs in the process of dehydrogenation of ethanol. These results allow understanding in detail the first steps of the ethanol oxidation on a specific catalytic surface Pt3Sn1, which is one of the most utilized catalytic mixtures based on Pt for DEFCs.

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