Kinetics-Controlled Synthesis of {100}-Facet-Enclosed Gold Quasi-Square Nanosheets with Curved Edges

Graphical Planar gold nanocrystals with a non-conventional quasi-square morphology, mainly enclosed with {100} facets, were successfully prepared via glutathione-mediated one-pot synthesis under kinetics control, exhibiting an enhanced electrochemical activity for methanol oxidation in alkaline medium. We report the preparation of gold (Au) nanosheets with a quasi-square morphology and curved edges (Au QSNSs). The atomic packing on the edge, corner, and central part of an individual Au QSNS is carefully observed via spherical aberration corrected high-resolution transmission electron microscopy, and the atomic-resolution images confirm the dominant presence of {100} facets on all these regions. Such type of two-dimensional nanostructure is of great interest, as conventional gold nanoplates/nanoprisms are mainly enclosed with {111} facets on upper/bottom faces. The use of glutathione and octadecyltrimethylammonium chloride as the shape-directing agent and the capping agent, respectively, at appropriate amounts, together with a dropwise addition of Au precursor at controlled rate, have been validated to be crucial for the formation of such a unique two-dimensional nanostructure. When acting as electrocatalysts for the methanol oxidation reaction in alkaline medium, the Au QSNSs/C exhibited noticeable enhancement, compared to spherical counterparts, in terms of mass activity, reaction kinetics, and long-term durability, demonstrating their structural advantage.