Density Functional Investigation of the Adsorption of Ethanol–Water Mixture on the Pt(111) Surface

Abstract

Steam reforming of ethanol–water mixture is a promising renewable route to obtain hydrogen; however, our atomistic understanding of the interaction of ethanol–water mixture with transition-metal surfaces is far from satisfactory. In this work, we report a density functional theory investigation of the adsorption properties of the ethanol–water mixture on the Pt(111) surface employing semilocal exchange-correlation functional within nonlocal van der Waals corrections. From our calculations and analysis, we found that water molecules are located near the surface instead of ethanol, which is in contrast with our initial expectation based on the large magnitude of the adsorption energy of ethanol on Pt(111) compared with water/Pt(111). We found that the formation of hydrogen bonds among ethanol–ethanol, water–water, and ethanol–water molecules plays an important role in the adsorbate structure of the ethanol–water mixture on Pt(111), in particular, due to the enhancement of the binding energy of the hydrogen bonds induced by the interaction with the Pt(111) surface. We found that the van der Waals correction does not strongly affect the adsorbate structures of the ethanol–water mixture; however, as expected, it enhances the adsorption energy, which is coverage-dependent. Furthermore, we also report results and analysis for the adsorption of ethanol and water molecules on the Pt(111).

Glycerol adsorption on a defected Pt6/Pt(100) substrate: a density functional theory investigation within the D3 van der Waals correction

“…As found in previous DFT studies with vdW corrections, 22,27,28 the D3 vdW correction increases the adsorption energy. For example, the enhancement factor that is dened as the ratio between the PBE+D3 and PBE adsorption energies ranges from 2.25 to 2.80 for glycerol on the low-coordinated Pt 6 sites.…”

“…These results are supported by our previous ndings for alcohol molecules on close-packed TM surfaces. 22,27,28 As expected, the adsorbed structures in which glycerol binds on the terrace sites, e.g., structures F and G, are similar to the adsorbed structure with glycerol bound on the clean Pt(100) surface, that is, d O-Pt is 2.31 A and 2.33Å for structure F and the structure with glycerol bound on the clean Pt(100) surface, respectively.…”

“…26 To improve the description of the long range non-local correlation effects, which play a crucial role in weak interacting systems such as water and ethanol adsorption on TM(111), 27,28 and glycerol adsorption on Pt surfaces, 22 we employed one of the van der Waals (vdW) corrections proposed by S. Grimme, namely, the D3 vdW correction. [29][30][31] The D3 vdW framework has been employed with great success in several studies.…”

“…This procedure was employed in previous studies. 27,28 Although the number of congurations is relatively small, it provides a route to improve our atomistic understanding of the interaction of glycerol with defected Pt(100) substrates. Finally, those congurations were reoptimized using the PBE+D3 functional to take into account the vdW corrections.…”

Influence of structural parameters on the reaction of low temperature ethanol steam reforming over Pt/Al2O3 catalysts

“…Depending on the nature of the metal, the ethoxide intermediate formed during ethanol adsorption, is either converted to an adsorbed oxametallacycle (favored over Ru or Rh catalysts) or to adsorbed acetaldehyde (favored over Pt or Pd catalysts) [49][50][51], with both conformations suggesting coordination to multiple surface atoms. On the other hand it has been reported that ethanol adsorption geometry is strongly modified over hydrated or hydroxylated surfaces [48,52,53]. In the former case, ethanol does not interact directly with metallic surface, but with the pre-adsorbed water molecule, resulting in an acetaldehyde molecule, H-bonded with the water molecule and with the C O bond being almost parallel to the surface.…”