Nanoscale morphological evolution of monocrystalline Pt surfaces during cathodic corrosion
| Autor: | Marc T. M. Koper, Nakkiran Arulmozhi, Thomas J. P. Hersbach |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Multidisciplinary
Materials science self-similar growth chemistry.chemical_element musculoskeletal system Corrosion Cathodic protection Anode cathodic corrosion Monocrystalline silicon Metal Chemistry chemistry electrochemistry visual_art Physical Sciences visual_art.visual_art_medium platinum Composite material Facet Platinum Single crystal |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America |
| ISSN: | 1091-6490 |
| Popis: | Significance Cathodic corrosion is a relatively unexplored but highly enigmatic electrochemical phenomenon that transforms, roughens, and dissolves metal surfaces under cathodic polarization. We show how cathodic corrosion of a platinum spherical single-crystal electrode in an aqueous alkaline electrolyte leads initially to the formation of etch pits that reflect the local symmetry of the surface and subsequently develop into a growth regime in which self-similar diffusion-limited patterns emerge. These are unique observations that may eventually open the door to controlled surface patterning and nanoparticle preparation. This paper studies the cathodic corrosion of a spherical single crystal of platinum in an aqueous alkaline electrolyte, to map out the detailed facet dependence of the corrosion structures forming during this still largely unexplored electrochemical phenomenon. We find that anisotropic corrosion of the platinum electrode takes place in different stages. Initially, corrosion etch pits are formed, which reflect the local symmetry of the surface: square pits on (100) facets, triangular pits on (111) facets, and rectangular pits on (110) facets. We hypothesize that these etch pits are formed through a ternary metal hydride corrosion intermediate. In contrast to anodic corrosion, the (111) facet corrodes the fastest, and the (110) facet corrodes the slowest. For cathodic corrosion on the (100) facet and on higher-index surfaces close to the (100) plane, the etch pit destabilizes in a second growth stage, by etching faster in the (111) direction, leading to arms in the etch pit, yielding a concave octagon-shaped pit. In a third growth stage, these arms develop side arms, leading to a structure that strongly resembles a self-similar diffusion-limited growth pattern, with strongly preferred growth directions. |
| Databáze: | OpenAIRE |
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