Functional MXene Materials: Progress of Their Applications.

Nowadays, two-dimensional materials have many applications in materials science. As a novel two-dimensional layered material, MXene possesses distinct structural, electronic, and chemical properties; thus, it has potential applications in many fields, including battery electrodes, energy storage materials, sensors, and catalysts. Up to now, more than 70 MAX phases have been reported. However, in contrast to the variety of MAX phases, the existing MXene family merely includes Ti2 C, Ti3 C2 , (Ti1/2 , Nb1/2 )2 C, (V1/2 , Cr1/2 )3 C2 , Nb2 C, Ti3 CN, Ta4 C3 , V2 C, and Nb4 C3 . Among these materials, the Ti3 C2 Tx MXene exhibits prominently high volumetric capacitance, and the rate at which it transports electron is suitable for electrode materials in batteries and supercapacitors. Hence, Ti3 C2 Tx is commonly utilized as an electrode material in ion batteries such as Li+ , Na+ , K+ , Mg2+ , Ca2+ , and Al3+ batteries. What is more, Ti2 C has the biggest specific surface area among all of these potential MXene phases, and therefore, Ti2 C has remarkably high gravimetric hydrogen storage capacities. In addition, Ti2 CO2 materials display extremely high activity for CO oxidation, which makes it possible to design catalysts for CO oxidation at low temperatures. Furthermore, Ti3 C2 Tx with O, OH, and/or F terminations can be used for water purification owing to excellent water permeance, favorable filtration ability, and long-time operation ability. This review supplies a relatively comprehensive summary of various applications of MXenes over the past few years.