Atomic Level Understanding of the Structural Stability and Catalytic Activity of Nanoporous Gold/Titania Cluster Inverse Catalysts at Ambient and High Temperatures.

Abstract

Nanoporous gold (NPG) exhibits exceptional catalytic performance at low temperatures, but its activity declines at elevated temperatures due to structural coarsening. Loading metal oxide nanoparticles onto NPG can enhance its catalytic activity at high temperatures. In this work, we used NPG-supported titania nanoparticles as a model system (denoted as Ti2O4/NPG) to study their catalytic activity at ambient and high temperatures with CO oxidation as a probe reaction by density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD) simulations. The possible factors that may affect the CO oxidation reaction pathways and energy profiles on the Ti2O4/NPG, such as oxygen vacancies; silver impurities; Mars-van Krevelen (MvK), Eley-Rideal (ER), or trimolecular Eley-Rideal (TER) mechanisms; and catalytic active sites, were comprehensively investigated. The results showed that reaction energy barriers on Ti2O4/NPG were not significantly decreased compared to the pristine NPG, indicating that their catalytic activities at ambient temperature were comparable. At the evaluated temperature (400 °C), the Ti2O4/NPG exhibited superior thermal stability and maintained its active sites, while the NPG reduced active sites due to surface coarsening. The strong oxide-metal interaction (SOMI) effect between the NPG and Ti2O4 nanoparticles is found to be a main factor for the high structural stability and catalytic activity at high temperatures.