Bimetallic Nanoparticle Oxidation in Three Dimensions by Chemically Sensitive Electron Tomography and in Situ Transmission Electron Microscopy

Abstract

The formation of hollow-structured oxide nanoparticles is primarily governed by the Kirkendall effect. However, the degree of complexity of the oxidation process multiplies in the bimetallic system because of the incorporation of more than one element. Spatially dependent oxidation kinetics controls the final morphology of the hollow nanoparticles, and the process is highly dependent on the elemental composition. Currently, a theoretical framework that can predict how different metal elements result in different oxide morphologies remains elusive. In this work, utilizing a combination of state-of-the-art in situ environmental transmission electron microscopy and three-dimensional (3D) chemically sensitive electron tomography, we provide an in situ and 3D investigation of the oxidation mechanism of the Ni-Fe nanoparticles. The direct measurements allow us to correlate the 3D elemental segregation in the particles with the oxidation morphologies, that is, single-cavity or dual-cavity hollow structure, and multicavity porous structures. Our findings in conjunction with theoretical calculations show that metal concentration, diffusivity, and particle size are important parameters that dictate the mechanical and phase stabilities of the hollow oxide shell, which in turn determine its barrier properties and the final hollow oxide morphology. It sheds light on how to use multielemental oxidation to control morphology in nanomaterials and demonstrates the power of 3D chemical imaging.

Identification of Key Reversible Intermediates in Self‐Reconstructed Nickel‐Based Hybrid Electrocatalysts for Oxygen Evolution

“…The heterogenization process strengthens the contact and consolidation of initial Ni 3 N nanoparticles (Figure b), which is beneficial to electron transfer. Further transmission electron microscopy (TEM) investigations reveal the internal porous structure of NiNPS nanoparticles in Figure c (Supporting Information, Figure S2), resulting from the different ion migration rate during reaction, which contributes to a higher electrochemical surface area. The obvious lattice distances of 0.407 and 0.222 nm in Figure d agree well with the d‐spacing of the (100) plane of Ni 3 N and (111) plane of Ni 2 P, respectively, confirming the formation of surface heterostructure.…”

A Nano-Micro Engineering Nanofiber for Electromagnetic Absorber, Green Shielding and Sensor

“…Figure 2 d shows the TEM images of hollow oxide particles with different diameters of 17.80, 18.61, and 16.69 nm. (ii) For shells with cracks, oxygen can enter the shell through the cracks, and the metal core is locally oxidized to form multiple cavities [ 54 ]. Figure 2 e shows the presence of multiple-cavity in one oxide particle with the diameter ranging from 8.10 to 14.51 nm.…”

“…The thin oxide shell acts as a template to support subsequent reactions. (i) For continuous shells, due to the Kirkendall effect that diffusion coefficient of Ni/Co is higher compared to oxygen, the central metal atoms can diffuse outward through the shell and are oxidized, generating a hollow particle with an expanding cavity [51][52][53][54]. Figure 2d shows the TEM images of hollow oxide particles with different diameters of 17.80, 18.61, and 16.69 nm.…”

Identification of Key Reversible Intermediates in Self‐Reconstructed Nickel‐Based Hybrid Electrocatalysts for Oxygen Evolution

“…Theh eterogenization process strengthens the contact and consolidation of initial Ni 3 Nn anoparticles ( Figure 1b), which is beneficial to electron transfer. Further transmission electron microscopy (TEM) investigations reveal the internal porous structure of NiNPS nanoparticles in Figure 1c (Supporting Information, Figure S2), resulting from the different ion migration rate during reaction, [23,24] which contributes to ah igher electrochemical surface area. Theo bvious lattice distances of 0.407 and 0.222 nm in Figure 1dagree well with the d-spacing of the (100) plane of Ni 3 Na nd (111) plane of Ni 2 P, respectively, confirming the formation of surface heterostructure.F urther energy-dispersive X-ray analysis (EDX) demonstrates the specific elemental distributions of Ni, N, P, and S( Figure 1e).…”