Freestanding Penta-Twinned\nPd–Ag Nanosheets

2D metal nanosheets have attracted significant attention\nas efficient\ncatalysts for various important chemical reactions. However, the development\nof metal nanosheets with controlled compositions and morphologies\nhas been slow due to the challenges associated with synthesizing thermodynamically\nunfavorable 2D structures. Herein, we report a synthesis route of\nfreestanding Pd–Ag penta-twinned nanosheets (Pd–Ag ptNSs)\nwith distinct 5-fold twin boundaries. Through the coreduction of Ag\nand Pd precursors on presynthesized Pd ptNSs, Ag could be homogeneously\nalloyed with Pd, leading to the formation of well-defined Pd–Ag\nptNSs. The promotional effects of the bimetallic composition, 2D structure,\nand twin boundaries on catalysis were studied by using Pd–Ag\nptNS-catalyzed H<sub>2</sub> production from formic acid decomposition\nas a model reaction. Notably, the catalytic activity of the Pd–Ag\nptNSs drastically outperformed those of monometallic, bimetallic,\nand 3D counterparts, such as Pd ptNSs, Pd–Ag nanosheets without\na TB, and Pd–Ag octahedral nanocrystals, demonstrating the\npromising potential of the integration of twin boundaries and multiple\ncompositions in the development of high-performance 2D nanocatalysts.