In‐Plane Chemical Ordering (Mo2/3R1/3)2AlB2 (R = Tb, Dy, Ho, Er, Tm, and Lu) i‐MAB Phases and their Two‐Dimensional Derivatives (MBene): Synthesis, Structure, Magnetic, and Supercapacitor Performance

Abstract A family of hexagonal in‐plane chemical ordering (Mo 2/3 R 1/3 ) 2 AlB 2 ( R = Tb, Dy, Ho, Er, Tm, and Lu) i ‐MAB phases are synthesized with R‐3m hexagonal structure. The i ‐MAB phases with R = Tb to Tm are considered to have a nonlinear ferromagnetic‐like coupling magnetic ground state with gradually weakened magnetocrystalline anisotropy due to variant R‐R distances and 4 f electrons. Their 2D derivatives (2D‐MBene) with rare‐earth ( R ) atom vacancies are obtained by chemical etching. The delamination solvent, surface functional terminations, and chemical bond of 2D‐MBene can be modified by one‐step nitridation in environment‐friendly nitrogen instead of ammonia. A phase conversion is caused by nitridation at 973 K from 2D‐MBene to Mo 2 N, leading to the optimized specific capacitance of 229 F g −1 . Besides exploring more rare‐earth‐containing laminated boride systems, this work also demonstrates the promising application of their 2D derivatives with R vacancies in supercapacitors.