S, N co-doped rGO/fluorine-free Ti3C2Tx aerogels for high performance all-solid-state supercapacitors

The development of fluorine-free MXene based composites for electrochemical energy storage and conversion devices is considered to be a promising approach. Herein, we used Lewis acid Fe (III) to etch Ti3AlC2 successfully to prepare MXene with in-situ loaded Fe2O3 nanoparticles. The three-dimensional porous aerogels co-doped with S and N were synthesized by the redox self-assembly reaction of MXene and graphene oxide in the hydrothermal condition containing thiourea. XPS results show that S and N heteroatoms can enhance the hydrophilicity and pseudo-capacitance of the composites by changing the electronic structure of adjacent C atoms and forming S-C/ N-C bonds. The specific capacitance of the optimized Fe3+-Ti3C2Tx/S,N-rGO-2 is 220.7 F g-1 at 1 A g-1, and the capacitance retention rate is above 80 % after 5000 cycles at a current density of 6 A g-1. The all-solid-state symmetric supercapacitor with Fe3+-Ti3C2Tx/S,N-rGO-2 as electrode materials, and PVA-KOH as electrolyte can work normally in extreme environments of 60 and-20 degrees C, respectively. This work provides a viable route for the fluorine-free preparation of MXene and its electrochemical application.