Theoretical Investigation on the Au-Anchor Site in Phosphate-Doped Au/Al<sub>2</sub>O<sub>3 </sub>Catalysts

Abstract

In order to clarify the Au-anchor site in phosphate-doped Al2O3 and investigate the mechanism of Au-stabilization by phosphate, density functional theory (DFT) calculations were carried out. We calculated Au atom adsorption onto three model surfaces, such as sAl2O3 (a stoichiometric Al2O3 surface), fPO–Al2O3 (an Al2O3 surface fully covered by phosphate), and pPO–Al2O3 (an Al2O3 surface partially covered by phosphate). The calculated results showed that the order of stability for Au atom adsorption onto these three model surfaces is Au/fPO-Al2O3 > Au/pPO-Al2O3 > Au/sAl2O3. When Au atom adsorbs to a phosphate-phosphate bridge site of fPO-Al2O3 surface, the stabilization of Au adsorption onto the surface is especially large (the adsorption energy of Au is −3.16 eV). This high stability of Au at the phosphate-phosphate bridge site is due to negative charge transfer from Au to Al2O3 surface, which makes Au–O bond more stable. Hence, we have concluded that “phosphate-phosphate bridge sites” anchor Au. [DOI: 10.1380/ejssnt.2015.380]