Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Abstract

Active sites and catalytic activity of heterogeneous catalysts is determined by their surface atomic structures. However, probing surface structure at atomic resolution is difficult especially for solution ensembles of catalytic nanocrystals which consist of heterogeneous particles with irregular shapes and surfaces. Here, we constructed 3D maps of coordination number (CN) and generalized CN ( CN ) for individual surface atoms of sub-3 nm Pt nanocrystals. Our results reveal that the synthesized Pt nanocrystals are enclosed by islands of atoms with non-uniform shapes that lead to complex surface structures, including a high ratio of low-coordination surface atoms, reduced domain size of low-index facets, and various types of exposed high-index facets. 3D maps of CN are directly correlated to catalytic activities assigned to individual surface atoms with distinct local coordination structures, which explains the origin of high catalytic performance of small Pt nanocrystals in important reactions such as oxygen reduction reaction and CO electro-oxidation.

Direct strain correlations at the single-atom level in three-dimensional core-shell interface structures

“…A clear facet-dependence can be observed from the ORR activity (Fig. 3f and Supplementary Movie 4 ), showing much higher ORR activity for {111} facets compared to that of {100} and {110} facets, as expected from the known big difference between the ORR activity of different facets 14 , 22 , 23 (Supplementary Fig. 4 ).…”

“…However, studies to date have been mostly limited to ensemble-averaged structure or lower dimensional (2D) imaging, which cannot provide the full 3D atomic structural detail of the core-shell interface 4 , 7 , 17 , 19 , 20 . Due to the intrinsic limitation of 2D projection-based analyses, most of the studies have only focused on cubic-shaped nanoparticles terminated by {100} facets 17 , 19 – 21 , although {111} facets are technologically more important for their superior catalytic properties, for example, in the case of Pt-based catalysts 14 , 22 , 23 . Also, misfit strain not only affects the structure of the shell but can also propagate into the core.…”

Tracking the 3D atomic structures during thermal treatment and catalytic activity of individual Pt nanoparticles

“…Figure 2a shows the changes in the fractions of the coordination number (CN), which is an index to evaluate the local atomic environments. We divided the atomic local environments into four classes in accordance with the CN 29 : CN = 12, CN = 10-11, CN = 9 − 7, and CN ≤ 6. Each environment shows different behaviour with elapsed time, especially in the initial stage.…”

Complex ligand adsorption on 3D atomic surfaces of synthesized nanoparticles investigated by machine-learning accelerated ab initio calculation

“…Realistic 3D atomic structures of individual single-crystalline Pt nanoparticles were obtained by the Brownian one-particle reconstruction method 18,19 , revealing that structures of the PVPpassivated Pt nanoparticles are nonuniformly deviated from the bulk face-centered-cubic structure of Pt (Figures 1a,b). Surface structures of the synthesized Pt nanoparticles are complicated due to the irregular shapes of islands, resulting in diverse distribution of generalized coordination number (CN ���� ) that indicates distinct local geometry of a surface atom (Figure 1a).…”