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

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.