Self-propagating fabrication of 3D porous MXene-rGO film electrode for high-performance supercapacitors

2D MXene nanosheets with metallic conductivity and high pseudo-capacitance are promising electrode materials for supercapacitors. Especially, MXene films can be directly used as electrodes for flexible supercapacitors. However, they suffer from sluggish ion transport due to self-restacking, causing limited electrochemical performance. Herein, a flexible 3D porous MXene film is fabricated by incorporating graphene oxide (GO) into MXene film followed by self-propagating reduction. The self-propagating process is facile and effective, which can be accomplished in 1.25 s and result in 3D porous framework by releasing substantial gas instantaneously. As the 3D porous structure provides massive ion-accessible active sites and promotes fast ion transport, the MXene-rGO films exhibit superior capacitance and rate performance. With the rGO content of 20%, the MXene-rGO-20 film delivers a high capacitance of 329.9 F g−1 at 5 mV s−1 in 3 M H2SO4 electrolyte and remains 260.1 F g−1 at 1,000 mV s−1 as well as good flexibility. Furthermore, the initial capacitance is retained above 90% after 40,000 cycles at 100 A g−1, revealing good cycle stability. This work not only provides a high-performance flexible electrode for supercapacitors, but also proposes an efficient and time-saving strategy for constructing 3D structure from 2D materials.