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  • Tailoring Structure, Compos...
    Persson, Ingemar; el Ghazaly, Ahmed; Tao, Quanzheng; Halim, Joseph; Kota, Sankalp; Darakchieva, Vanya; Palisaitis, Justinas; Barsoum, Michel W.; Rosen, Johanna; Persson, Per O. Å.

    Small (Weinheim an der Bergstrasse, Germany) 14, Številka: 17
    Journal Article

    The exploration of 2D solids is one of our time's generators of materials discoveries. A recent addition to the 2D world is MXenes that possses a rich chemistry due to the large parent family of MAX phases. Recently, a new type of atomic laminated phases (coined i‐MAX) is reported, in which two different transition metal atoms are ordered in the basal planes. Herein, these i‐MAX phases are used in a new route for tailoriong the MXene structure and composition. By employing different etching protocols to the parent i‐MAX phase (Mo2/3Y1/3)2AlC, the resulting MXene can be either: i) (Mo2/3Y1/3)2C with in‐plane elemental order through selective removal of Al atoms or ii) Mo1.33C with ordered vacancies through selective removal of both Al and Y atoms. When (Mo2/3Y1/3)2C (ideal stoichiometry) is used as an electrode in a supercapacitor—with KOH electrolyte—a volumetric capacitance exceeding 1500 F cm−3 is obtained, which is 40% higher than that of its Mo1.33C counterpart. With H2SO4, the trend is reversed, with the latter exhibiting the higher capacitance (≈1200 F cm−3). This additional ability for structural tailoring will indubitably prove to be a powerful tool in property‐tailoring of 2D materials, as exemplified here for supercapacitors. Using atomically resolved electron microscopy, it is shown that the chemically ordered atomic laminate (Mo2/3Y1/3)2AlC can be used to derive either i) an in‐plane vacancy ordered Mo1.33C MXene or ii) (Mo2/3Y1/3)2C MXene with in‐plane elemental order. These materials have different electrochemical properties, with in one case a capacitance value exceeding 1500 F cm−3.