The Influence of Oxygen Concentration during MAX Phases (Ti(3)AlC(2)) Preparation on the α-Al(2)O(3) Microparticles Content and Specific Surface Area of Multilayered MXenes (Ti(3)C(2)T(x))

The high specific surface area of multilayered two-dimensional carbides called MXenes, is a critical feature for their use in energy storage systems, especially supercapacitors. Therefore, the possibility of controlling this parameter is highly desired. This work presents the results of the influence of oxygen concentration during Ti(3)AlC(2) ternary carbide—MAX phase preparation on α-Al(2)O(3) particles content, and thus the porosity and specific surface area of the Ti(3)C(2)T(x) MXenes. In this research, three different Ti(3)AlC(2) samples were prepared, based on TiC-Ti(2)AlC powder mixtures, which were conditioned and cold pressed in argon, air and oxygen filled glove-boxes. As-prepared pellets were sintered, ground, sieved and etched using hydrofluoric acid. The MAX phase and MXene samples were analyzed using scanning electron microscopy and X-ray diffraction. The influence of the oxygen concentration on the MXene structures was confirmed by Brunauer-Emmett-Teller surface area determination. It was found that oxygen concentration plays an important role in the formation of α-Al(2)O(3) inclusions between MAX phase layers. The mortar grinding of the MAX phase powder and subsequent MXene fabrication process released the α-Al(2)O(3) impurities, which led to the formation of the porous MXene structures. However, some non-porous α-Al(2)O(3) particles remained inside the MXene structures. Those particles were found ingrown and irremovable, and thus decreased the MXene specific surface area.