Preparation and energy storage properties of V₂O₅/MXene nanocomposites

Supercapacitors are usually used in new energy storage devices, communication technology, military, and aerospace fields due to their long lifecycle and high power density. Presently, it is imperative to find the electrode materials with low cost and excellent capacity. MXenes have received increasing attention due to their unique physical and chemical properties. They not only have superior electrical conductivity but also contain abundant surface groups (−OH, −F or −O); therefore, they are regarded as versatile 2D materials. MXenes can generate higher volumetric capacitance than that of graphene. However, MXene nanosheets are inclined to stack together, limiting the electrochemical properties of supercapacitors. In this work, an MXene (Ti₃C₂T_x) was obtained by etching an MAX (Ti₃AlC₂) phase using HF. To expand the interlayer spacing of Ti₃C₂T_x, the liquid-phase intercalation method was adopted. After the interlayer spacing was expanded, V₂O₅ nanosheet (NSV) and V₂O₅ nanobelt (NBV) were loaded on the MXene surface by a facile hydrothermal process. Their structure and morphology were characterized using different techniques, such as X-ray diffraction, Brunauer–Emmett–Teller surface area measurements, and field-emission scanning electron microscopy. The results show that the interlayer spacing of MXene is increased after liquid-phase intercalation, and NSV and NBV are uniformly loaded on the MXene surface. Moreover, the specific surface areas of the NSV/MXene and NSV/MXene nanocomposites are higher than that of the MXene; therefore, the nanocomposites can provide more active sites for electrochemical reactions. The electrochemical performances of the nanocomposites were investigated in 1.0 mol·L⁻¹ Na₂SO₄ and 1.0 mol·L⁻¹ LiNO₃ aqueous solutions. The specific capacitances of V₂O₅, MXene, NSV/MXene, and NBV/MXene are 8.1, 15.7, 96.8, and 88.5 F·g⁻¹ in 1.0 mol·L⁻¹ Na₂SO₄, respectively. When they are tested in 1.0 mol·L⁻¹ LiNO₃, their specific capacitances are 64.6, 46.7, 180.0, and 114.0 F·g⁻¹, respectively. Therefore, the NSV/MXene nanocomposite is a potential electrode material for supercapacitors.