Density Functional Calculations of the Sequential Adsorption of Hydrogen on Single Atom and Small Clusters of Pd and Pt Supported on Au(111)

Abstract

We have used density functional theory calculations to study the sequential adsorption of hydrogen on Pd and Pt atomic site catalysts such as single atom alloy catalyst (SAAC), single atom catalyst (SAC), and single clusters catalyst (SCC) of on Au(111). The results show that Pd systems tend to have nearzero free energy of hydrogen adsorption (Δ 𝐺𝐻𝑎𝑑𝑠 ≈0) under various coverage conditions of adsorbed hydrogen. In the case of Pt systems, Δ 𝐺𝐻𝑎𝑑𝑠 ≈0 only at high coverage conditions of adsorbed hydrogen.Such differences come from the preference of hydrogen for high-coordination and low-coordination sites on Pd and Pt, respectively. The low coordination of hydrogen results in multiple adsorption sites with Δ 𝐺𝐻𝑎𝑑𝑠 ≈0 in SCC of Pt/Au. These results can help understand the different catalytic properties of Pd/Au and Pt/Au.