Defect-driven selective metal oxidation at atomic scale

Qi Zhu,Langli Luo,Zhiliang Pan,Ze Zhang,Jiangwei Wang,Chaolun Ni,Guang Cao,Frederic Sansoz,Hua Wei,Zhiyu Zhao

doi:10.1038/s41467-020-20876-9

Abstract

Nanoscale materials modified by crystal defects exhibit significantly different behaviours upon chemical reactions such as oxidation, catalysis, lithiation and epitaxial growth. However, unveiling the exact defect-controlled reaction dynamics (e.g. oxidation) at atomic scale remains a challenge for applications. Here, using in situ high-resolution transmission electron microscopy and first-principles calculations, we reveal the dynamics of a general site-selective oxidation behaviour in nanotwinned silver and palladium driven by individual stacking-faults and twin boundaries. The coherent planar defects crossing the surface exhibit the highest oxygen binding energies, leading to preferential nucleation of oxides at these intersections. Planar-fault mediated diffusion of oxygen atoms is shown to catalyse subsequent layer-by-layer inward oxide growth via atomic steps migrating on the oxide-metal interface. These findings provide an atomistic visualization of the complex reaction dynamics controlled by planar defects in metallic nanostructures, which could enable the modification of physiochemical performances in nanomaterials through defect engineering.

Highlights

Nanoscale materials modified by crystal defects exhibit significantly different behaviours upon chemical reactions such as oxidation, catalysis, lithiation and epitaxial growth
Since the reaction dynamics at twin boundaries (TBs) play an important role in subsequent structural evolution and functionality of metallic nanomaterials[10,12,13], an atomic-scale understanding of this coherent defect contribution to chemical/electrochemical reactivity in nanomaterials is of general significance
Subsequent inward growth of the oxide is governed by the promoted oxygen diffusion along the planar defects that intersect with the oxide–metal interface, leading to layer-by-layer oxidation

Summary

Introduction

Nanoscale materials modified by crystal defects exhibit significantly different behaviours upon chemical reactions such as oxidation, catalysis, lithiation and epitaxial growth. Planar-fault mediated diffusion of oxygen atoms is shown to catalyse subsequent layer-by-layer inward oxide growth via atomic steps migrating on the oxide-metal interface These findings provide an atomistic visualization of the complex reaction dynamics controlled by planar defects in metallic nanostructures, which could enable the modification of physiochemical performances in nanomaterials through defect engineering. Recent studies of nanotwinned metallic nanoparticles attributed their superior catalytic performance to low-coordinated atomic steps, large tension, and high density of negative charges on the surface, which are critically affected by the presence of TBs16–20 These studies suggest that coherent TBs act as preferential sites for selective chemical/electrochemical reactions and as channels for fast atom transport[19,21]. These findings provide atomistic visualization and mechanistic understanding of defect-assisted reaction dynamics in nanoscale metals, which has direct ramifications for the development of advanced nanomaterials through defect engineering

Methods

Results

Conclusion