The Wet‐Oxidation of a Cu(111) Foil Coated by Single Crystal Graphene

Abstract

The wet‐oxidation of a single crystal Cu(111) foil is studied by growing single crystal graphene islands on it followed by soaking it in water. 18O‐labeled water is also used; the oxygen atoms in the formed copper oxides in both the bare and graphene‐coated Cu regions come from water. The oxidation of the graphene‐coated Cu regions is enabled by water diffusing from the edges of graphene along the bunched Cu steps, and along some graphene ripples where such are present. This interfacial diffusion of water can occur because of the separation between the graphene and the “step corner” of bunched Cu steps. Density functional theory simulations suggest that adsorption of water in this gap is thermodynamically stable; the “step‐induced‐diffusion model” also applies to graphene‐coated Cu surfaces of various other crystal orientations. Since bunched Cu steps and graphene ripples are diffusion pathways for water, ripple‐free graphene is prepared on ultrasmooth Cu(111) surfaces and it is found that the graphene completely shields the underlying Cu from wet‐oxidation. This study greatly deepens the understanding of how a graphene‐coated copper surface is oxidized, and shows that graphene completely prevents the oxidation when that surface is ultrasmooth and when the graphene has no ripples or wrinkles.

Cu-Modified La2Si2O7/TiO2 composite materials: preparation, characterization and photothermal properties

“…1(a) is around 250 nm, while there are some uncoated TiO 2 scattered around, and the surface of spherical SiO 2 is smooth while the surface of SiO 2 @TiO 2 is rough as can be seen from Fig. 1(d We can observe a 0.213 nm spacing with lattice stripes attributed to the (132) face of the tetragonal phase La 2 Si 2 O 7 , and 0.208 nm and 0.236 nm stripes corresponding to the (111) 23 and (040) faces of Cu and TiO 2 , respectively, and this result is consistent with the analysis of Fig. 2(a) XRD.…”

Eliminating the Galvanic Corrosion Effect of Graphene Coating by an Accurate and Rapid Self‐Assembling Defect Healing Approach

“…We have shown in this work that PFOT can accurately heal multiple-scale and multiple-type structural defects in the monolayer CVD graphene coating grown on Cu through a selfassembly process within just 15 min, which can effectively improve the corrosion resistance of graphene coating. With the underlying microscopic mechanisms revealed by systematic experimental measurements and DFT calculations, we can readily expect that this work can shed much light on the corrosion studies of many other related graphene systems, for example, multilayer graphene coating, [11,21,61,62] graphene wrinkles, [62][63][64][65] and graphene islands. [65] It has been shown that in a multilayer graphene coating, the defects in each layer will be covered by the neighboring layers, generating a labyrinth effect and prolonging the diffusion pathways of corrosive agents, which tends to improve the corrosion resistance comparing to the monolayer counterpart.…”

“…With the underlying microscopic mechanisms revealed by systematic experimental measurements and DFT calculations, we can readily expect that this work can shed much light on the corrosion studies of many other related graphene systems, for example, multilayer graphene coating, [11,21,61,62] graphene wrinkles, [62][63][64][65] and graphene islands. [65] It has been shown that in a multilayer graphene coating, the defects in each layer will be covered by the neighboring layers, generating a labyrinth effect and prolonging the diffusion pathways of corrosive agents, which tends to improve the corrosion resistance comparing to the monolayer counterpart. [11,21] However, the defects of CVD graphene are not easy to be fully covered, and the corrosion enhancement efficiency usually is limited (e.g., two-to fivefold [11,21,61] ).…”

“…For large-scale defects (e.g., large cracks and holes) in multilayer graphene that expose the substrate surface, PFOT molecules not only can readily passivate the exposed substrate metal, but also can passivate the reactive defect edges in different layers. In addition, CVD graphene coatings frequently have wrinkles, [62][63][64][65] or there may be large separation between the graphene coating and possible substrate-surface step corners. [65] These weak points will provide many facile transport channels for corrosive agents (e.g., H 2 O molecule), leading to the extensive corrosion of the metal substrates and even breakdown of the graphene coating.…”

“…In addition, CVD graphene coatings frequently have wrinkles, [62][63][64][65] or there may be large separation between the graphene coating and possible substrate-surface step corners. [65] These weak points will provide many facile transport channels for corrosive agents (e.g., H 2 O molecule), leading to the extensive corrosion of the metal substrates and even breakdown of the graphene coating. It may be promising for PFOT to effectively passivate the ingression gates of these transport channels, for example, the edge-front sites of graphene islands on Cu, [65] because PFOT molecule can effectively passivate the Cu atoms at the defectedge sites (C5 and C6 configurations in Figure 3) and inhibit the ingression of environmental substances into the graphene/ substrate interface.…”