Defect engineering is considered as one of the most efficient strategies to regulate the electronic structure of materials and involves the manipulation of the types, concentrations, and spatial distributions of defects, resulting in unprecedented properties. It is shown that a single-layered MnO2 nanosheet with vacancies is a robust half-metal, which was confirmed by theoretical calculations, whereas vacancy-free single-layered MnO2 is a typical semiconductor. The half-metallicity of the single-layered MnO2 nanosheet can be observed for a wide range of vacancy concentrations and even in the co-presence of Mn and O vacancies. This work enables the development of half-metals by defect engineering of well-established low-dimensional materials, which may be used for the design of next-generation paper-like spintronics.

As the properties of ultrathin two-dimensional (2D) crystals are strongly related to their electronic structures, more and more attempts were carried out to tune their electronic structures to meet the high standards for the construction of next-generation smart electronics. Herein, for the first time, we show that the conductive nature of layered ternary chalcogenide with formula of Cu2 WS4 can be switched from semiconducting to metallic by hydrogen incorporation, accompanied by a high increase in electrical conductivity. In detail, the room-temperature electrical conductivity of hydrogenated-Cu2 WS4 nanosheet film was almost 10(10) times higher than that of pristine bulk sample with a value of about 2.9×10(4)  S m(-1) , which is among the best values for conductive 2D nanosheets. In addition, the metallicity in the hydrogenated-Cu2 WS4 is robust and can be retained under high-temperature treatment. The fabricated all-solid-state flexible supercapacitor based on the hydrogenated-Cu2 WS4 nanosheet film shows promising electrochemical performances with capacitance of 583.3 F cm(-3) at a current density of 0.31 A cm(-3) . This work not only offers a prototype material for the study of electronic structure regulation in 2D crystals, but also paves the way in searching for highly conductive electrodes.

Defect engineering is considered as one of the most efficient strategies to regulate the electronic structure of materials and involves the manipulation of the types, concentrations, and spatial distributions of defects, resulting in unprecedented properties. It is shown that a single-layered MnO 2 nanosheet with vacancies is a robust half-metal, which was confirmed by theoretical calculations, whereas vacancyfree single-layered MnO 2 is a typical semiconductor. The halfmetallicity of the single-layered MnO 2 nanosheet can be observed for a wide range of vacancy concentrations and even in the co-presence of Mn and O vacancies. This work enables the development of half-metals by defect engineering of well-established low-dimensional materials, which may be used for the design of next-generation paper-like spintronics.Half-metals, with a metallic nature for one spin and an insulating/semiconducting nature for the opposite spin, are considered as ideal materials for applications in spintronics, because their carriers are theoretically 100 % spin-polarized. [1,2] To date, various half-metals have been reported, which are mainly based on bulk oxides, Heusler alloys, or perovskites, whereas attention has rarely been paid to the half-metallicity in low-dimensional materials.