报告题目：The Latest Developments in Synthesis and Applications of Two-Dimensional Carbides
Two-dimensional (2D) solids– the thinnest materials available to us – offer unique properties and a potential path to device miniaturization. The most famous example is graphene, which is an atomically thin layer of carbon atoms bonded together in-plane with sp2 bonds. In 2011, an entirely new family of 2Dsolids –transition metal carbides (Ti2C, Ti3C2, Nb4C3, etc.) and carbonitrides– was discovered by Drexel University scientists . Selective etching of the A-group element from a MAX phase results in formation of 2D Mn+1Xnsolids, labeled “MXene”. 17 different carbides and carbonitrides have been reportedto date [2-5].A new sub-family of multi-element ordered MXenes was discovered recently . Structure and properties of numerousMXenes have been predicted by the density functional theory, showing that MXenescan be metallic or semiconducting, 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 moleculescan intercalate MXenes leading to an increase of theirc lattice parameter . When dimethyl sulfoxide or TBAOH 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 such as batteries, Li-ion capacitors and supercapacitors [3-5]. Cations ranging from Na+ to Mg2+ and Al3+ intercalate MXenes. Ti3C2paper electrodes, produced by vacuum assisted filtration of an aqueous dispersion of delaminated Ti3C2, showa higher capacity than graphite anodes and also can be charged/discharged at significantly higher rates. They also demonstrate very high intercalation capacitance (up to 900 F/cm3) in aqueous electrolytes .
1. M. Naguib, et al, Advanced Materials, 23 (37), 4207-4331 (2011)
2. B. Anasori, et al, ACSNano(October 2015)
3. O. Mashtalir, et al, Nature Communication, 4, 1716 (2013)
4. M M. Ghidiu, Nature, 516, 78–81 (2014)
5. M. Naguib, Y. Gogotsi, Accounts of Chemical Research, 48 (1), 128-135 (2015)
Yury Gogotsi is Distinguished University Professor and Trustee Chair of Materials Science and Engineering at Drexel University. He is the founding Director of the A.J. Drexel Nanomaterials Institute and Associate Editor of ACS Nano. He works on nanostructured carbons and two-dimensional carbides for energy related and biomedical applications. His work on selective extraction synthesis of carbon and carbide nanomaterials with tunable structure and porosity had a strong impact on the field of capacitive energy storage. He has co-authored 2 books, more than 400 journal papers and obtained more than 50 patents. He has received numerous national and international awards for his research. He was recognized as Highly Cited Researcher by Thomson-Reuters in 2014 and 2015, and elected a Fellow of AAAS, MRS, ECS and ACerS and a member of the World Academy of Ceramics.