Unveiling the Dynamic Oxidative Etching Mechanisms of Nanostructured Metals/Metallic Oxides in Liquid Media Through In Situ Transmission Electron Microscopy

Oxidative etching in nanostructured metals and metallic oxides plays a fundamental role in numerous areas of chemical synthesis and materials processing for the semiconductor industry. An in-depth understanding of the oxidative etching mechanisms is of great significance to design various fascinating nanomaterials for practical application. In situ liquid cell transmission electron microscopy (TEM) has the merits of high temporal and spatial resolutions in real-time, and thus it can provide solid evidence directly for the dynamic evaluation of oxidative etching in nanostructured materials that occur in solution. Herein, the recent progress of oxidative etching in nanostructured metals and metallic oxides is overviewed. First, the advancements in liquid cells designs are briefly introduced for in situ TEM observation. Subsequently, in situ liquid cell TEM/STEM advances for the oxide etching mechanisms in different surface chemistry surroundings are systematically described. In addition, both the galvanic replacement and electrochemical etching reactions are also discussed. Finally, the challenges and opportunities in utilizing the in situ liquid cell TEM technique to visualize a specific dynamic oxidative etching process are proposed. This review will provide deep insights into dynamic changes in oxidative etching processes of nanostructured materials and assist in formulating design rules for developing high-end advanced devices.