Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States.
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States.
J Am Chem Soc. 2022 Aug 31;144(34):15698-15708. doi: 10.1021/jacs.2c05989. Epub 2022 Aug 17.
Cathodic corrosion represents an enigmatic electrochemical process in which metallic electrodes corrode under sufficiently reducing potentials. Although discovered by Fritz Haber in the 19th century, only recently has progress been made in beginning to understand the atomistic mechanisms of corroding bulk electrodes. The creation of nanoparticles as the end-product of the corrosion process suggests an additional length scale of complexity. Here, we studied the dynamic evolution of morphology, composition, and crystallographic structural information of nanocrystal corrosion products by analytical and four-dimensional electrochemical liquid-cell scanning transmission electron microscopy (EC-STEM). Our operando/in situ electron microscopy revealed, in real-time, at the nanometer scale, that cathodic corrosion yields significantly higher levels of structural degradation for heterogeneous nanocrystals than bulk electrodes. In particular, the cathodic corrosion of Au nanocubes on bulk Pt electrodes led to the unexpected formation of thermodynamically immiscible Au-Pt alloy nanoparticles. The highly kinetically driven corrosion process is evidenced by the successive anisotropic transition from stable Pt(111) bulk single-crystal surfaces evolving to energetically less-stable (100) and (110) steps. The motifs identified in this microscopy study of cathodic corrosion of nanocrystals are likely to underlie the structural evolution of nanoscale electrocatalysts during many electrochemical reactions under highly reducing potentials, such as CO and N reduction.
阴极腐蚀是一种神秘的电化学过程，其中金属电极在足够还原的电势下腐蚀。尽管阴极腐蚀是由弗里茨·哈伯（Fritz Haber）在 19 世纪发现的，但直到最近才在开始理解腐蚀体电极的原子机制方面取得了进展。纳米颗粒作为腐蚀过程的最终产物的出现表明了复杂性的额外长度尺度。在这里，我们通过分析和四维电化学液体池扫描透射电子显微镜（EC-STEM）研究了纳米晶体腐蚀产物的形态、组成和晶体结构信息的动态演变。我们的在位/原位电子显微镜实时在纳米尺度上揭示了，与体电极相比，阴极腐蚀会导致异质纳米晶体的结构降解水平显著更高。特别是，在块状 Pt 电极上的 Au 纳米立方体的阴极腐蚀导致了出乎意料的形成热力学不相容的 Au-Pt 合金纳米颗粒。高度动力学驱动的腐蚀过程由稳定的 Pt(111)体单晶表面从稳定的 Pt(111)体单晶表面连续各向异性转变为能量较低稳定的(100)和(110)台阶来证明。在这种对纳米晶体阴极腐蚀的显微镜研究中确定的图案很可能是在许多在高度还原电势下的电化学反应中，例如 CO 和 N 还原，纳米尺度电催化剂的结构演变的基础。
