Free-standing 3D porous energy hydrogels enabled by ion-induced gelation strategy for High-performance supercapacitors

Two-dimensional (2D) materials, such as MXene and graphene, are considered as the ideal alternative electrode materials for high energy density supercapacitors. However, the inevitable collapsing and restacking problems caused by the van der Waals force will reduce their active surface sites and slow down the rate of ion transportation and thus cause the degradation of electrochemical performance. Hence, in this paper, we reported a facile and environment-friendly method to synthesize 3D Ti3C2Tx/rGO hybrid composite through an ion-induced gelation approach. With the assistance of Fe2+, Ti3C2Tx and rGO nanosheets converge to form a 3D porous Ti3C2Tx/rGO-Fe hydrogel with a high specific surface area of 59.5 m2 g−1. By optimizing the ratio of MXene and rGO, the resultant Ti3C2Tx/rGO-Fe electrode displays a maximum specific capacitance of 3194 mF cm−2 at 1 mA cm−2. Meanwhile, the assembled Ti3C2Tx/rGO-Fe//Ti3C2Tx/rGO-Fe symmetric supercapacitor delivers a maximum energy density of 76.3 μWh cm−2 at a power density of 500 μW cm−2 and unparalleled cycling performance with 95.6 % capacitance retention after 5000 cycles at 6 mA cm−2. This work demonstrates that the ion-induced gelation method for preparing 3D MXene/rGO hydrogel has great potential in applying high-performance electrode materials for supercapacitors.