提交时间: 2017-05-02
摘要: Liquid-phase exfoliation of tetraethylammonium graphite intercalation compound [TEA-GIC] has been prepared by high-power tip-sonication of graphite in aqueous TEA solution. The release of gaseous species due to the decomposition of TEA under microwave irr
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: A lithium-assisted approach has been developed for the exfoliation of pristine graphite, which allows the large-scale preparation of few-layer graphene nanosheets. The process involves an unexpected physical insertion and exfoliation, and the graphene nanosheets prepared by this method reveal undisturbed sp2-hybridized structures. A possible two-step mechanism, which involves the negative charge being trapped around the edges of the graphite layers and a subsequent lithiation process, is proposed to explain the insertion of lithium inside the graphite interlayers. If necessary, the present exfoliation can be repeated and thinner (single or 2–3 layer) graphene can be achieved on a large scale. This simple process provides an efficient process for the exfoliation of pristine graphite, which might promote the future applications of graphene.
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-05-09
摘要: Density functional theory (DFT) calculation is employed to study the adsorption properties of Pb and Cu on recently synthesized two-dimensional materials MXenes, including Ti3C2, V2C1 and Ti2C1. The influence of surface decoration with functional groups such as H, OH and F have also been investigated. Most of these studied MXenes exhibit excellent capability to adsorb Pb and Cu, especially the adsorption capacity of Pb on Ti2C1 is as high as 2560 mg g 1. Both the binding energies and the adsorption capacities are sensitive to the functional groups attached to the MXenes’ surface. Ab initio molecular dynamics (ab-init MD) simulation confirms that Ti2C1 remains stable at room temperature after adsorbing Pb atoms. Our calculations imply that these newly emerging two-dimensional MXenes are promising candidates for wastewater treatment and ion separation.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: MXenes, a novel family of two-dimensional metal carbides, are receiving intense attention for lithium-ion batteries (LIBs) and super- capacitors because they have high volumetric capacitance exceeding all carbon materials. However, serious interlayer stacking exists in MXene particles, which greatly decreases the electrical conductivity in the bulk and hinders the accessibility of interlayers to electrolyte ions. Thus, multi-stacked MXene particles exhibit low capacitance and poor rate capability. Herein, we report an effective strategy to directly improve the electrochemical performance of multi-stacked MXene (Ti3C2Tx) particles as LIB anode materials. It was successfully realized by growing conductive “carbon nanofiber (CNF) bridges” within the gaps of each Ti3C2Tx particle as well as the outside. With the help of these CNFs, the as-prepared Ti3C2/CNF particles exhibited signifi- cantly improved reversible capacity compared with pure Ti3C2Tx particles. More remarkably, even at an ultrahigh rate of 100 C, the capacity of Ti3C2/CNF hybrid particles was just slightly lower than that of pure Ti3C2Tx particles at 1 C, and there was no capacity decay after 2900 cycles at 100 C, demonstrating excellent rate capability and superior long-term stability at the ultrahigh rate.