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

In this work, we achieved a novel preparation of Ti3C2 MXene (MXene-DES) with few layers anda highdegree of hydroxylation by a deep eutectic solvent (DES)-assistedelectrochemical ultrasonic composite exfoliation method which is easyto scale up. The electrochemical process used a mixture of low-costDES (choline chloride-urea) and water as the electrolyte, inwhich DES acts as a triple role of intercalation, interlayer expansion,and anti-oxidation. DES attached to the surface and interlayer oflayered Ti3C2 formed an antioxidative protectivecover, resulting in the layered Ti3C2 beinggrafted with hydroxyl functional groups instead of forming TiO2 in water during the entire exfoliation process. The preparedMXene-DES exhibits fewer layers, larger interlayer spacing,higher degree of hydroxylation, and stronger oxidation resistancethan the MXene prepared by traditional ultrasound in a nitrogen atmosphere(MXene-N-2). The symmetric flexible solid-state supercapacitorbased on an activated carbon electrode and the composite gel polymerelectrolyte composed of MXene-DES, DES, and polyvinyl alcoholexhibits good mechanical properties, a wide voltage window of 2.3V, and a high specific capacitance of 133.7 F center dot g(-1) (0.1 A center dot g(-1)). Our strategy paved a simple,low-cost, and relatively environmentally friendly way to the scalablepreparation and application of antioxidative high-quality MXene.

Automated summary

In this work, we developed a new method for the preparation of Ti3C2 MXene (MXene-DES) with few layers and a high degree of hydroxylation. The method involved the use of a deep eutectic solvent (DES)-assisted electrochemical ultrasonic composite exfoliation, which is easy to scale up. The MXene-DES exhibited improved properties compared to MXene-N-2, including fewer layers, larger interlayer spacing, higher degree of hydroxylation, and stronger oxidation resistance. This strategy provides a simple, low-cost, and environmentally friendly approach to the scalable preparation and application of antioxidative high-quality MXene.