Environmental stability is a key property for catalysts exposed to air, which necessitates an understanding of the early-stage interactions between catalyst surfaces and gasses, such as Cu and O2. Furthermore, the interplay between the oxidation mechanisms and various forms of surface defects that are present in all realistic surfaces is largely unknown. Environmental Transmission Electron Microscopy (ETEM) studies show that different types of Cu surface defects, such as facets, consistently produce different nucleation and growth patterns of non-uniform copper oxide islands. To understand the underpinnings of the oxidation mechanisms, atomistic simulations depicting oxygen adsorption and activation barrier energies are needed. However, comprehensive early-stage kinetic data is not available over broad sets of Cu surface defects. In this talk, we develop an approach based on in situ ETEM and atomistic simulations to describe the early stages of oxidation of faceted Cu surfaces. Our study is focused on Cu(100), Cu(110), and Cu(111) surfaces with facet edge and corner type defects, as well as grain boundary defects. Our results indicate that a small anisotropy over different O diffusion paths is present on Cu(100) and Cu(111) surfaces facets, as well as that less preferential O diffusion occurs over Cu(100) and Cu(111) facet features. In contrast, strongly preferential O adsorption on and diffusion along Cu(110) step edges is consistently observed. ETEM in situ experiments under various environmental conditions and temperatures agree with these conclusions, demonstrating highly preferential Cu oxide formation on Cu(110) surface features and more consistent oxide formation on Cu(100) and Cu(111) features. Correlation of these experimental and simulation results characterizes the interplay between O diffusion kinetics and structural defects, aiding in the predictive design of Cu-rich catalytic materials and possibly leading to a paradigm shift in the current understanding of oxidation.

Influence of surface defects on copper oxidation via coordinated in situ ETEM and atomistic simulation methods

253rd National Meeting (2017)

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