Computational study of intrinsic defects on the electronic properties and quantum capacitance of Sc2CF2 monolayer

Defects are unavoidable in the synthesis of the materials and usually play the important role in tailoring the properties of two-dimensional materials. In this paper, the electronic properties and quantum capacitance of Sc2CF2 MXene with intrinsic defect are investigated theoretically. Sc2CF2-dSc -> C is energetically more favorable than other systems. Pristine Sc2CF2 is an indirect semiconductor. Sc2CF2-dC -> F, Sc2CF2-dC -> Sc, Sc2CF2-dF -> Sc, and Sc2CF2-dSc -> C undergo the semiconductor-metal transition due to the introduction of intrinsic defect. The appearance of defect energy level results in the direct bandgap of 0.2 eV for Sc2CF2-dSc -> F and spin-polarized semiconductor for Sc2CF2-dF -> C. Sc2CF2 and Sc2CF2-dF -> C monolayers are potential cathode materials in aqueous system, while Sc2CF2-dC -> F, Sc2CF2-dC -> Sc, Sc2CF2-dF -> Sc, Sc2CF2-dSc -> C, and Sc2CF2-dSc -> F monolayers are suitable for anode materials, especially for Sc2CF2-dF -> Sc. The extension of voltage does not change the electrode type of the systems except Sc2CF2-dSc -> F monolayer. The work function and Bader charge are further analyzed.