Two-dimensional Mo _1.33C MXene with divacancy ordering prepared from parent 3D laminate with in-plane chemical ordering

Abstract

The exploration of two-dimensional solids is an active area of materials discovery. Research in this area has given us structures spanning graphene to dichalcogenides, and more recently 2D transition metal carbides (MXenes). One of the challenges now is to master ordering within the atomic sheets. Herein, we present a top-down, high-yield, facile route for the controlled introduction of ordered divacancies in MXenes. By designing a parent 3D atomic laminate, (Mo _2/3Sc _1/3) ₂AlC, with in-plane chemical ordering, and by selectively etching the Al and Sc atoms, we show evidence for 2D Mo _1.33C sheets with ordered metal divacancies and high electrical conductivities. At ∼1,100 F cm ⁻³, this 2D material exhibits a 65% higher volumetric capacitance than its counterpart, Mo ₂C, with no vacancies, and one of the highest volumetric capacitance values ever reported, to the best of our knowledge. This structural design on the atomic scale may alter and expand the concept of property-tailoring of 2D materials.

Abstract

Vacancies in 2D materials can influence their properties, however controlling their formation remains a challenge. Here the authors show that selective etching of a 3D laminate with in-plane chemical ordering results in formation of MXenes with ordered divacancies, as well as elevated conductance and supercapacitance.