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Two-dimensional (2D) MoTe2 nanomaterials have emerged as a promising candidate for constructing excellent supercapacitors due to their high capacitive performance. Recent studies have revealed that MoTe2 has broad prospects as an active material in supercapacitors, although its strict requirements in terms of the external environment and complex preparation process remain serious obstacles to its practical application. Toward this end, MoTe2 nanosheets (NSs) were prepared by a facile and inexpensive liquid-phase exfoliation approach for the fabrication of MoTe2 electrodes. The results show that the MoTe2 NSs exhibit significantly improved electrochemical performance, with a specific capacitance (859 F g−1) more than three times that of bulk MoTe2 (271 F g−1) at a current density of 1 A g−1. In addition, the MoTe2-based electrode showed excellent cycle stability and maintained excellent specific capacitance (92.7% of the initial value) after 1000 cycles under the working condition of a current density of 10 A g−1. This study describes a fundamental investigation on the energy storage and conversion properties of 2D layered materials.

Van der Waals (vdW) heterostructure, vertically assembled by two kinds of two-dimensional layered materials with extraordinary electronic and optical properties, has emerged as an interesting candidate in the applications of electronics and optoelectronics. It is known that vacancies are crucial in determining the physical properties of materials, and always exist in the materials during the process of actual experimental preparations and can be artificially introduced. In the present work, the structures and electronic properties of a black phosphorus/molybdenum disulfide (BP/MoS2) vdW heterostructure with P atom vacancies are investigated via first principles calculations. Based on the structural symmetry, two types of heterostructures with single-atom vacancy and three types of heterostructures with diatomic vacancies are constructed. It is found that the presence of a single P atom vacancy leads to the transformation from semiconductor to metal in the BP/MoS2 heterostructure, which is mainly due to the contribution of the remaining P atomic p orbitals based on analyses of the partial density of states (PDOS). On the other hand, the heterostructures with diatomic P atom vacancies still maintain their pristine semiconductor features, along with a decrease in their bandgap value. In addition, the plane electrostatic potential indicates that the introduction of P atom vacancy defects causes a change in the electrostatic potential of the BP atomic layer, resulting in asymmetric electrostatic potential on both sides of the BP layer. Finally, it is interesting to note that the accumulation-depletion of electrons occurs around the vacancy, but also partially emerges at the MoS2 layer. Our results provide the possibility for the application of 2D-vacancy-defect heterostructure systems.