2D Carbides and Nitrides of Transition Metals (MXenes): Synthesis, Structure and Energy Storage Applications
Wednesday, August 26, 2015
11:30 am - 1:00 pm
Hudson Hall 125
Two-dimensional (2D) solids offer unique properties and a potential path to device miniaturization. The most famous example is graphene. Recently, an entirely new family of 2D solids ¿ transition metal carbides and carbonitrides ¿ was discovered by Drexel University scientists [1,2]. Selective etching of the A-group element from a MAX phase results in formation of 2D Mn+1Xn solids, labeled ¿MXene¿. 17 different carbides and carbonitrides have been produced to date [2-5]. Structure and properties of numerous MXenes have been predicted by the density functional theory, showing that MXenes can be metallic or semiconducting (up to 2 eV band gap), depending on their surface termination. Their elastic constants along the basal plane are expected to be higher than that of the binary carbides. Oxygen or OH terminated MXenes, are hydrophilic, but electrically conductive. Hydrazine, urea and other polar organic molecules can intercalate MXenes leading to an increase of the c lattice parameter of MXenes . When dimethyl sulfoxide was intercalated into Ti3C2, followed by sonication in water, a stable colloidal solution of single- and few-layer flakes was produced. One of the many potential applications for 2D Ti3C2 is in electrical energy storage devices[3-5]. Cations ranging from Na+ to Mg2+ and Al3+ intercalate MXenes. Ti3C2 paper electrodes show a higher capacity than graphite anodes and also can be charged/discharged at significantly higher rates.