Elucidating Cathodic Corrosion Mechanisms with Operando Electrochemical Transmission Electron Microscopy

Area of Science:

• Electrochemistry
• Materials Science
• Nanotechnology

Background:

• Cathodic corrosion, a process where metals degrade under reducing potentials, was discovered by Fritz Haber.
• Understanding the atomistic mechanisms of bulk electrode corrosion is recent, with nanoparticles forming as corrosion products.
• Nanocrystal corrosion introduces complexity at an additional length scale.

Purpose of the Study:

• To investigate the dynamic evolution of morphology, composition, and crystallographic structure of nanocrystal corrosion products.
• To compare the structural degradation of heterogeneous nanocrystals versus bulk electrodes during cathodic corrosion.
• To elucidate the mechanisms underlying the structural evolution of nanoscale electrocatalysts under highly reducing potentials.

Main Methods:

• Analytical and four-dimensional electrochemical liquid-cell scanning transmission electron microscopy (EC-STEM).
• Operando/in situ electron microscopy for real-time, nanoscale observation.
• Study of cathodic corrosion of gold (Au) nanocubes on bulk platinum (Pt) electrodes.

Main Results:

• Cathodic corrosion of heterogeneous nanocrystals shows higher structural degradation than bulk electrodes.
• Unexpected formation of thermodynamically immiscible gold-platinum (Au-Pt) alloy nanoparticles.
• Kinetically driven corrosion leads to anisotropic transitions from stable Pt(111) surfaces to less stable (100) and (110) steps.

Conclusions:

• The identified motifs in nanocrystal cathodic corrosion are crucial for understanding nanoscale electrocatalyst structural evolution.
• This research provides insights into processes relevant to CO2 and N2 reduction reactions under highly reducing potentials.
• The study highlights the unique degradation pathways of nanocrystals compared to bulk materials in electrochemical environments.