Leiden Institute of Chemistry, Leiden University, 2300 RA Leiden, The Netherlands.
Leiden Institute of Chemistry, Leiden University, 2300 RA Leiden, The Netherlands
Proc Natl Acad Sci U S A. 2020 Dec 22;117(51):32267-32277. doi: 10.1073/pnas.2017086117. Epub 2020 Dec 7.
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.
本文研究了在碱性水溶液中球形单晶铂的阴极腐蚀，以详细描绘在这个仍在很大程度上未被探索的电化学现象中形成的腐蚀结构的详细面各向异性依赖性。我们发现，铂电极的各向异性腐蚀发生在不同的阶段。最初，腐蚀蚀坑形成，反映了表面的局部对称性：（100）面的正方形蚀坑，（111）面的三角形蚀坑，以及（110）面的矩形蚀坑。我们假设这些蚀坑是通过三元金属氢化物腐蚀中间产物形成的。与阳极腐蚀不同，（111）面腐蚀最快，（110）面腐蚀最慢。对于（100）面和靠近（100）面的较高指数表面上的阴极腐蚀，在第二生长阶段，蚀坑由于在（111）方向更快地腐蚀而变得不稳定，导致蚀坑中的臂状结构，形成凹八角形坑。在第三生长阶段，这些臂状结构发展出侧臂，导致一种强烈类似于自相似扩散限制生长模式的结构，具有强烈的优先生长方向。
