Reshaping Dynamics of Gold Nanoparticles under H₂ and O₂ at Atmospheric Pressure

Abstract

Despite intensive research eorts, the nature of the active sites for O 2 and H 2 adsorption/dissociation by supported gold nanoparticles (NPs) is still an unresolved issue 1 in heterogeneous catalysis. This stems from the absence of a clear picture of the evolution of the structural properties of Au NPs in the presence of these gases at near reaction conditions, i.e. at high pressures and high temperatures. We hereby report on the rst real-space observation of the equilibrium shapes of TiO 2 -supported model Au NPs under O 2 and H 2 at atmospheric pressure using window gas cell transmission electron microscopy (GCTEM). In situ GCTEM observations show instantaneous changes in the equilibrium shape of Au NPs under O 2 during cooling from 400°C to room temperature. In comparison, no instant change in equilibrium shape is observed under H 2 environment. To interpret these experimental observations, the equilibrium shape of Au NPs under O 2 , atomic oxygen and H 2 gas environments was predicted using a multiscale structure reconstruction model. Excellent agreement between GCTEM observations and theoretical modelling under O 2 provides strong evidence for the molecular adsorption of O 2 on the Au NPs below 120°C. Molecular adsorption takes place on specic Au facets which are identied in this work. In the case of H 2 , theoretical modelling predicts weak interactions with gold atoms which explain their high morphological stability under this gas. This work provides atomic structural information for the fundamental understanding of the O 2 and H 2 adsorption properties of Au NPs under real working conditions and also shows a new way to identify the active sites of heterogeneous nanocatalysts under reaction conditions by monitoring the structure reconstruction.

Nanoparticle enhanced combination therapy for stem-like progenitors defined by single-cell transcriptomics in chemotherapy-resistant osteosarcoma

“…Some studies have revealed that NPs may exhibit a tendency to aggregate in the liver. 26,27 In our study, in vivo imaging indicated a high uptake of NP DiR in the liver, whereas other organs showed minimal uptake of the NPs. To evaluate the consequence of NP accumulation in the liver, H&E staining of the main tissues from SJSA-1 tumor-bearing mice ( Supplementary Fig.…”

Selective shortening of gold nanorods: when surface functionalization dictates the reactivity of nanostructures

“…45 More theoretical details and comparisons with other DFT functional could be found in our previous works. 46,47 The electronic structure of the adsorption systems was analyzed through Bader charge density analysis 48 with the implementation of Henkelman and co-workers 49 which allows analyzing the density issued from VASP code. From a theoretical point of view, classic DFT cannot accurately capture weak interactions such as van der Waals forces and it is always difficult to ascertain the existence of a physisorbed molecular state on the gold surfaces.…”

Multiscale atomistic simulation of metal nanoparticles under working conditions

“…2a). 50 The observed reshaping gives rm evidence that the Au NPs offer direct adsorption sites for the molecular oxygen under the conditions of atmospheric pressure and at room temperatures, which is crucial for understanding the CO oxidation mechanism on supported Au NPs under real conditions. For supported metal NPs under reaction conditions, the simulation of the structure of Pt/SrTiO 3 (110) was successfully performed under similar conditions to those of the in situ ETEM experiments.…”