More Like this

1. High-throughput density functional theory screening of double transition metal MXene precursors

   https://doi.org/10.1038/s41597-023-02755-2  

   Nykiel, Kat; Strachan, Alejandro (November 2023, Scientific Data)

   Abstract MXenes are an emerging class of 2D materials of interest in applications ranging from energy storage to electromagnetic shielding. MXenes are synthesized by selective etching of layered bulk MAX phases into sheets of 2D MXenes. Their chemical tunability has been significantly expanded with the successful synthesis of double transition metal MXenes. While knowledge of the structure and energetics of double transition metal MAX phases is critical to designing and optimizing new MXenes, only a small subset of these materials been explored. We present a comprehensive dataset of key properties of MAX phases obtained using density functional theory within the generalized gradient approximation exchange-correlation functionals. Energetics and structure of 8,712 MAX phases have been calculated and stored in a queryable, open database hosted at nanoHUB. 

   more » « less
2. Vanadium MXenes materials for next-generation energy storage devices

   https://doi.org/10.1088/1361-6528/acc539  

   Sijuade, Ayomide Adeola; Eze, Vincent Obiozo; Arnett, Natalie Y; Okoli, Okenwa I (April 2023, Nanotechnology)

   Abstract Batteries and supercapacitors have emerged as promising candidates for next-generation energy storage technologies. The rapid development of new two-dimensional (2D) electrode materials indicates a new era in energy storage devices. MXenes are a new type of layered 2D transition metal carbides, nitrides, or carbonitrides that have drawn much attention because of their excellent electrical conductivity, electrochemical and hydrophilic properties, large surface area, and attractive topological structure. This review focuses on various synthesis methods to prepare vanadium carbide MXenes with and without etchants like hydrofluoric acid, lithium fluoride, and hydrochloric acid to remove the ‘A’ layers of the MAX phase. The goal is to demonstrate the utilization of a less toxic etching method to achieve MXenes of comparable properties to those prepared by traditional methods. The influence of intercalation on the effect of high interlayer spacing between the MXene layers and the performance of MXenes as supercapacitor and battery electrodes is also addressed in this review. Lastly, the gaps in the current knowledge for vanadium carbide MXenes in synthesis, scalability, and utilization in more energy storage devices were discussed. 

   more » « less
3. Topochemical synthesis of 2D materials

   https://doi.org/10.1039/c8cs00649k  

   Xiao, Xu; Wang, Hao; Urbankowski, Patrick; Gogotsi, Yury (November 2018, Chemical Society Reviews)

   Since the demonstration of the unique properties of single-layer graphene and transition metal dichalcogenides (TMDs), research on two-dimensional (2D) materials has become one of the hottest topics, with the family of 2D materials quickly expanding. This expansion is mainly attributable to the development of new synthesis methods to create new materials. This review will summarize and critically analyze topochemical synthesis methods for synthesizing novel 2D materials. For example, the emerging family of 2D transition metal carbides, nitrides and carbonitrides (MXenes) are synthesized primarily by selective etching of “A” (metal) elements from MAX phases. Another 2D material, hydrogenated germanene is produced by selective etching of calcium digermanide (CaGe 2 ). The topochemical transformation of one dichalcogenide into another and 2D oxides into 2D carbides or nitrides have attracted great attention because materials with many useful and diverse properties can be obtained by these methods. Topochemical synthesis methods provide alternative ways of synthesizing 2D materials not requiring van der Waals bonded solid precursors or vapor phase deposition, but they have not been comprehensively reviewed. In this review, we describe common principles of topochemical synthesis of 2D materials, explain synthesis mechanisms and offer an outlook for future research. 

   more » « less
4. The Evolution of MXenes Conductivity and Optical Properties Upon Heating in Air

   https://doi.org/10.1002/smtd.202300568  

   Shamsabadi, Ahmad A.; Fang, Hui; Zhang, Danzhen; Thakur, Anupma; Chen, Cindy Y.; Zhang, Aixi; Wang, Haonan; Anasori, Babak; Soroush, Masoud; Gogotsi, Yury; et al (July 2023, Small Methods)

   Abstract MXenes, a family of 2D transition‐metal carbides and nitrides, have excellent electrical conductivity and unique optical properties. However, MXenes oxidize in ambient conditions, which is accelerated upon heating. Intercalation of water also causes hydrolysis accelerating oxidation. Developing new tools to readily characterize MXenes’ thermal stability can enable deeper insights into their structure–property relationships. Here, in situ spectroscopic ellipsometry (SE) is employed to characterize the optical properties of three types of MXenes (Ti₃C₂T_x, Mo₂TiC₂T_x, and Ti₂CT_x) with varied composition and atomistic structures to investigate their thermal degradation upon heating under ambient environment. It is demonstrated that changes in MXene extinction and optical conductivity in the visible and near‐IR regions correlate well with the amount of intercalated water and hydroxyl termination groups and the degree of oxidation, measured using thermogravimetric analysis. Among the three MXenes, Ti₃C₂T_xand Ti₂CT_x, respectively, have the highest and lowest thermal stability, indicating the role of transition‐metal type, synthesis route, and the number of atomic layers in MXene flakes. These findings demonstrate the utility of SE as a powerful in situ technique for rapid structure–property relationship studies paving the way for the further design, fabrication, and property optimization of novel MXene materials. 

   more » « less
5. 2D molybdenum and vanadium nitrides synthesized by ammoniation of 2D transition metal carbides (MXenes)

   https://doi.org/10.1039/c7nr06721f  

   Urbankowski, Patrick; Anasori, Babak; Hantanasirisakul, Kanit; Yang, Long; Zhang, Lihua; Haines, Bernard; May, Steven J.; Billinge, Simon J.; Gogotsi, Yury (January 2017, Nanoscale)

   MXenes are a rapidly growing class of 2D transition metal carbides and nitrides, finding applications in fields ranging from energy storage to electromagnetic interference shielding and transparent conductive coatings. However, while more than 20 carbide MXenes have already been synthesized, Ti 4 N 3 and Ti 2 N are the only nitride MXenes reported so far. Here by ammoniation of Mo 2 CT x and V 2 CT x MXenes at 600 °C, we report on their transformation to 2D metal nitrides. Carbon atoms in the precursor MXenes are replaced with N atoms, resulting from the decomposition of ammonia molecules. The crystal structures of the resulting Mo 2 N and V 2 N were determined with transmission electron microscopy and X-ray pair distribution function analysis. Our results indicate that Mo 2 N retains the MXene structure and V 2 C transforms to a mixed layered structure of trigonal V 2 N and cubic VN. Temperature-dependent resistivity measurements of the nitrides reveal that they exhibit metallic conductivity, as opposed to semiconductor-like behavior of their parent carbides. As important, room-temperature electrical conductivity values of Mo 2 N and V 2 N are three and one order of magnitude larger than those of the Mo 2 CT x and V 2 CT x precursors, respectively. This study shows how gas treatment synthesis such as ammoniation can transform carbide MXenes into 2D nitrides with higher electrical conductivities and metallic behavior, opening a new avenue in 2D materials synthesis. 

   more » « less