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Abstract 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 (Mo 2/3 Y 1/3 ) 2 AlC, the resulting MXene can be either: i) (Mo 2/3 Y 1/3 ) 2 C with in‐plane elemental order through selective removal of Al atoms or ii) Mo 1.33 C with ordered vacancies through selective removal of both Al and Y atoms. When (Mo 2/3 Y 1/3 ) 2 C (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 Mo 1.33 C counterpart. With H 2 SO 4 , 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.
Persson et al. (2018) studied this question.