New Ti3-yNbyC2Tx MXenes as high-rate and ultra-stable electrode materials for supercapacitors

As a promising supercapacitor electrode material nowadays, the development of Ti3C2Tx has been limited by the demand for the high-rate performance and ultra-long cycling life up to one hundred thousand times. In the present work, new double transition metal Ti3-yNbyC2 T x MXenes were prepared for the first time by etching Ti3-yNbyAlC2 solid solution MAX precursors obtained via self-propagating high-temperature synthesis method. The received Ti3-yNbyC2Tx MXenes have larger interlayer spacing and more surface -O terminations compared to Ti3C2Tx, which renders that the double transition metal MXenes exhibit superior rate performance and high cycling stability as electrode materials for supercapacitors. In particular, Ti2.7Nb0.3C2Tx demonstrates a high volumetric specific capacity of 1336 F cm-3 at a scan rate of 2 mV s-1, superior rate performance with a volumetric specific capacity of 335 F cm-3 even at a scan rate of 2000 mV s-1, and ultra-long cycling life up to 84000 cycles at a current density of 10 A g-1. This work expands the family of MXenes and further provides a promising strategy to tailor the interlayer structure and chemistry ingredients of MXenes.