Electrochemical Properties of Ordered, Two-Dimensional, Double Transition Metals Carbides (MXenes)

Two dimensional (2D) transition metal carbides (MXenes) are a new family of nanomaterials with a very high potential as electrode materials for batteries and electrochemical capacitors (ECs). These materials are labeled MXene because they are obtained by selectively etching of the A-layers from their 3D layered, parent compounds the Mn+1AXn, or MAX, phases, where M is an early transition metal, A is an A-group element, such as Al or Si, X is carbon and/or nitrogen and n is 1 to 3. The excellent performance of MXenes as electrode materials for ECs was recently reported in the case of Ti3C2.1,2 Here, we report on the synthesis and electrochemical properties of the ordered MXenes, Mo2TiC2 and Mo2TiC3, wherein the Mo atoms are on the surface and the Ti atoms are between the Mo. The volumetric capacitance of freestanding electrodes fabricated by vacuum filtration of 2D Mo2TiC2 sheets, was about 400 F/cm3. (1) Lukatskaya, M. R.; Mashtalir, O.; Ren, C. E.; Dall’Agnese, Y.; Rozier, P.; Taberna, P. L.; Naguib, M.; Simon, P.; Barsoum, M. W.; Gogotsi, Y. Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide. Science (80-. ). 2013, 341, 1502–1505. (2) Ghidiu, M.; Lukatskaya, M. R.; Zhao, M.-Q.; Gogotsi, Y.; Barsoum, M. W. Conductive two-dimensional titanium carbide “clay” with high volumetric capacitance. Nature 2014, 516, 78–81.