Rational design of cobalt ion chelated quasi-monolayer Ti3C2Tx MXene with abundant surface loading for high-performance asymmetric supercapacitor

The cobalt ion chelated Ti3C2Tx MXene (Co@Ti3C2Tx MXene) composite is designed/prepared by alkalizing quasi-monolayer Ti3C2Tx MXene supernatant into -OH rich sample, followed by cobalt ion chelation, to achieve the high loading amount of Co element. The optimized Co@Ti3C2Tx MXene can display the high specific capacity of 48 mAh/g at the current density of 1 A/g, much higher than Ti3C2Tx MXene, which is attributed to the highly dispersed quasi-monolayer structure, additional Faradaic redox reaction of Co (Ⅱ/Ш), and enhanced conductivity from Co element. In terms of practical application, the assembled Co@Ti3C2Tx MXene//active carbon (AC) asymmetric supercapacitor device also exhibits the high energy density of 19 Wh/kg, and good cycle stability. The alkali modification/metal ion chelation is a simple and effective strategy to inhibit the stack and enhance electrochemical performances for Ti3C2Tx MXene.