The role of the anionic and cationic pt sites in the adsorption site preference of water and ethanol on defected Pt-4/Pt(111) substrates: A density functional theory investigation within the D3 van der waals corrections

Author(s)

Seminovski, Yohanna ^[1] ; Amaral, Rafael C. ^[1] ; Tereshchuk, Polina ^[1] ; Da Silva, Juarez L. F. ^[1]

Affiliation

^[1] Univ Sao Paulo, Sao Carlos Inst Chem, POB 780, BR-13560970 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Surface Science; v. 667, p. 84-91, JAN 2018.
• Web of Science Citations: 4

Abstract

Platinum (Pt) atoms in the bulk face-centered cubic structure have neutral charge because they are equivalent by symmetry, however, in clean Pt surfaces, the effective charge on Pt atoms can turn slightly negative (anionic) or positive (cationic) while increasing substantially in magnitude for defected (low-coordinated) Pt sites. The effective charge affect the adsorption properties of molecular species on Pt surfaces and it can compete in importance with the coupling of the substrate-molecule electronic states. Although several studies have been reported due to the importance of Pt for catalysis, our understanding of the role played by low-coordinated sites is still limited. Here, we employ density functional theory within the Perdew-Burke-Ernzerhof exchange-correlation functional and the D3 van der Waals (vdW) correction to investigate the role of the cationic and anionic Pt sites on the adsorption properties of ethanol and water on defected Pt-4/Pt(111) substrates. Four substrates were carefully selected, namely, two two-dimensional (2D) Pt-4 configurations (2D-strand and 2D-island) and two tridimensional (3D) Pt-4 (3D-fcc and 3D-hcp), to understand the role of coordination, effective charge, and coupling of the electronic states in the adsorption properties. From the Bader charge analysis, we identified the cationic and anionic sites among the Pt atoms exposed to the vacuum region in the Pt-4/Pt(111) substrates. We found that ethanol and water bind via the anionic O atoms to the low-coordinated defected Pt sites of the substrates, where the angle PtOH is nearly 100 degrees for most configurations. In the 3D-fcc or 3D-hcp defected configurations, the lowest-coordinated Pt atoms are anionic, hence, those Pt sites are not preferable for the adsorption of O atoms. The charge transfer from water and ethanol to the Pt substrates has similar magnitude for all cases, which implies similar Coulomb contribution to the adsorption energy. Moreover, we found a correlation of the adsorption energy with the shift of the center of gravity of the occupied d-states of Pt sites. (c) 2017 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 13/21045-2 - Theoretical prediction of the structure, thermodynamic stability, electronic, and reactivity properties of nanoclusters
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Regular Research Grants
• FAPESP's process: 14/02213-4 - A DENSITY FUNCTIONAL THEORY INVESTIGATION OF THE INTERACTION OF WATER AND ETHANOL WITH TRANSITION -METAL CLUSTERS SUPPORTED ON THE CeO2(hkl) SURFACES
• Grantee: Yohanna Seminóvski Pérez
• Support Opportunities: Scholarships in Brazil - Post-Doctoral