First-Principles Calculations of the Effect of γ-Alumina Surface Hydroxyl Structures on the Location and Dechlorination of a Platinum Precursor

The interaction between Pt precursors and alumina support is an important step in synthesizing Pt/Al₂O₃ catalysts, while an in-depth understanding of the interaction is still lacking. Herein, density functional theory (DFT) calculations were performed to simulate the coordination of H₂PtCl₆ with different surface hydroxyl groups, revealing the influence of the γ-Al₂O₃ surface hydroxyl structure on the position of the Pt precursor and the removal of Cl ligands. After drying, the interaction mechanism between [PtCl₆]^2- and alumina support involves hydrogen bonds and van der Waals forces, which are the main driving forces for the structural transformation from [PtCl₆]^2- coordinated with the surface hydroxyl group into the PtCl_x(OH)_y species (OH is the γ-Al₂O₃ surface group). HO-μ₁-Al_VI and H₂O-μ₁-Al_VI on the (100) surface with electrophilicity facilitate hauling and activating the electron-rich [PtCl₆]^2-, but the nucleophilic (110) surface has a weaker interaction with [PtCl₆]^2-. Combining free energy and electronic property analysis, the stable structures on the (100) surface after drying treatment are PtCl₄(OH)₂ and PtCl₃(OH)₃, while only PtCl₄(OH)₂ structures can be formed on the (110) surface. This study can deepen our understanding of the interaction mechanism between Al-hydroxyl groups and Pt precursors, providing a theoretical reference for the precise placement of Pt active phases and the construction of metal-support interfaces.