Stable carbon encapsulated titanium carbide MXene aqueous ink for fabricating high-performance supercapacitors

Ti-based MXenes have shown great promise in electrochemical applications, including (photo)electrocatalysis and energy storage. However, their practical application has been hindered by their rapid oxidation in the presence of water and O2. In this work, we propose a method to solve the problem through a one-step hydrothermal treatment of MXene (Ti3C2Tx, where Tx is –OH or –F) in the presence of agarose. The hydrothermal treatment results in the in situ capping of the phenolic carbon layer on the Ti3C2Tx to form Ti3C2Tx@C, which improves its chemical stability by protecting the Ti atoms from oxidation with water and O2, and thus enhances its electrochemical performance by avoiding re-stacking of the Ti3C2Tx@C sheets. The as-prepared Ti3C2Tx@C exhibits high oxidation resistance with >95% performance when stored in an aqueous medium for at least 100 days. Ti3C2Tx@C provides a specific capacitance of 736 F g–1 in 1 M H2SO4 electrolyte over a voltage window of 0.5 V. Having excellent water dispersibility and high electrochemical activity, Ti3C2Tx@C is ideal for the preparation of stable MXene inks for the fabrication of high-performance interdigitated electrodes through inkjet printing. The flexible micro-supercapacitor constructed from Ti3C2Tx@C ink exhibits excellent cyclic stability up to 10,000 charge-discharge cycles without a significant decrease in specific capacitance.