Regular Article

A DFT study of H₂ adsorption on Pd_n/SnO₂ (110) surfaces (n = 1−10)

¹ Instituto de Física del Sur (IFISUR), Departamento de Física, Universidad Nacional del Sur (UNS), CONICET, Av. L. N. Alem 1253, B8000CPB Bahía Blanca, Argentina
² Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, 47011 Valladolid, Spain
³ Instituto de Física del Sur (IFISUR), Departamento de Química, Universidad Nacional del Sur (UNS), CONICET, Av. L. N. Alem 1253, B8000CPB Bahía Blanca, Argentina

^a e-mail: egerman@uns.edu.ar

Received: 9 November 2018
Received in final form: 4 February 2019
Published online: 8 May 2019

Abstract

Hydrogen adsorption on palladium atoms pre-adsorbed on a tin oxide semiconductor has been studied and compared with H₂ adsorption on a bare SnO₂. By means of density functional theory calculations, the preferential number of Pd atoms and their geometry as well as the physisorption and chemisorption of H₂ is analyzed on these surfaces. Namely, bare stoichiometric SnO₂ (110) and Pd-doped SnO₂ (110) surface systems are considered. It is found that Pd atoms tend to form clusters composed of 5 atoms. When considering sites with a favorable adsorption energy ( >0.10 eV), these pre-adsorbed Pd₅ clusters increase the number of active sites for H₂ chemisorption from 5 – in the case of the bare surface – to 16 for the same surface area. Bare SnO₂ (110) surfaces also present 5 potential sites for physisorption while Pd₅/SnO₂ surface presents 10 potential physisorption sites when applying the same adsorption energy criterion. Although dissociative H₂ adsorption is energetically more favorable for bare SnO₂ than for Pd₅/SnO₂, the molecular H₂ adsorption is slightly more favorable for the doped system.