Preparation of Antioxidative MXene by Deep Eutectic Solvent-Assisted Electrochemical Ultrasonic Composite Exfoliation and Its Application in Flexible Solid-State Supercapacitors

Abstract

In this work, we achieved a novel preparation of Ti 3 C 2 MXene (MXene−DES) with few layers and a high degree of hydroxylation by a deep eutectic solvent (DES)-assisted electrochemical ultrasonic composite exfoliation method which is easy to scale up. The electrochemical process used a mixture of low-cost DES (choline chloride−urea) and water as the electrolyte, in which DES acts as a triple role of intercalation, interlayer expansion, and anti-oxidation. DES attached to the surface and interlayer of layered Ti 3 C 2 formed an antioxidative protective cover, resulting in the layered Ti 3 C 2 being grafted with hydroxyl functional groups instead of forming TiO 2 in water during the entire exfoliation process. The prepared MXene−DES exhibits fewer layers, larger interlayer spacing, higher degree of hydroxylation, and stronger oxidation resistance than the MXene prepared by traditional ultrasound in a nitrogen atmosphere (MXene−N 2 ). The symmetric flexible solidstate supercapacitor based on an activated carbon electrode and the composite gel polymer electrolyte composed of MXene−DES, DES, and polyvinyl alcohol exhibits good mechanical properties, a wide voltage window of 2.3 V, and a high specific capacitance of 133.7 F•g −1 (0.1 A•g −1 ). Our strategy paved a simple, low-cost, and relatively environmentally friendly way to the scalable preparation and application of antioxidative high-quality MXene.