A novel high-purity V 2 C MXene two-dimensional carbide, was successfully synthesized by etching V 2 AlC with sodium fluoride and hydrochloric acid at 90 • C for 72 h. From the analysis of X-ray diffraction, energy dispersive spectra, and X-ray photoelectron spectroscopy, the purity of as-synthesized V 2 C MXene was >90 wt% with a few impurities of Na 5 Al 3 F 14 and V 2 AlC. The V 2 C MXene made by this method was much purer than those made by HF etching at room temperature. The as-prepared V 2 C MXene showed excellent electrochemical properties as anode of lithium-ion batteries. The capacity can be 260 mAh g −1 if discharged under 370 mA g −1 . The capacity was increased with charge cycles at high charge rate (500 mA g −1 ). It was suggested that V 2 C with high purity can be promising anode material with excellent performance.
Two-dimensional carbide MXenes (Ti 3 C 2 T x and V 2 CT x ) were prepared by exfoliating MAX phases (Ti 3 AlC 2 and V 2 AlC) powders in the solution of sodium fluoride (NaF) and hydrochloric acid (HCl). The specific surface area (SSA) of as-prepared Ti 3 C 2 T x was 21 m 2 /g, and that of V 2 CT x was 9 m 2 /g. After intercalation with dimethylsulfoxide, the SSA of Ti 3 C 2 T x was increased to 66 m 2 /g; that of V 2 CT x was increased to 19 m 2 /g. Their adsorption properties on carbon dioxide (CO 2 ) were investigated under 0-4 MPa at room temperature (298 K). Intercalated Ti 3 C 2 T x had the adsorption capacity of 5.79 mmol/g, which is close to the capacity of many common sorbents. The theoretical capacity of Ti 3 C 2 T x with the SSA of 496 m 2 /g was up to 44.2 mmol/g. Additionally, due to high pack density, MXenes had very high volume-uptake capacity. The capacity of intercalated Ti 3 C 2 T x measured in this paper was 502 V·v -1 . This value is already higher than volume capacity of most known sorbents. These results suggest that MXenes have some advantage features to be researched as novel CO 2 capture materials. suitable material to adsorb and capture CO 2 .In general, pressure and/or temperature swing approaches are used to capture CO 2 in porous materials. The porous materials, as CO 2 sorbents, should have superior properties in terms of capacity, stability, kinetics, selectivity, and regeneration [1]. Up to now, a wide range of sorbents for CO 2 capture, have been used and studied, including metal organic frameworks (MOFs) [2], functionalized porous silica [3], activated carbon [4], zeolites [5], metal oxides, and microporous polymers [6]. Among these sorbents, MOFs exhibit very high CO 2 uptake up to 54.4 mmol/g under high pressures (5 MPa) at 298 K [2]. Despite the excellent adsorption capacities, MOFs are much more expensive 238
Here a novel material for methane adsorption was synthesized and studied, which is a graphene-like twodimensional (2D) carbide (Ti 2 C, a member of MXenes), formed by exfoliating Ti 2 AlC powders in a solution of lithium fluoride (LiF) and hydrochloric acid (HCl) at 40°C for 48 h. Based on first-principles calculation, theoretically perfect Ti 2 C with O termination has a specific surface area (SSA) of 671 m 2 g -1 and methane storage capacity is 22.9 wt%. Experimentally, 2.85 % exfoliated Ti 2 C with mesopores shown methane capacity of 11.58 cm 3 (STP: 0°C, 1 bar) g -1 (0.82 wt%) under 5 MPa and the SSA was 19.1 m 2 g -1 . For Ti 2 C sample intercalated with NH 3 ÁH 2 O, the adsorbed amount was increased to 16.81 cm 3 (STP) g -1 at same temperature. At the temperature of 323 K, the adsorbed amount of as-prepared Ti 2 C was increased to 52.76 cm 3 (STP) g -1 . For fully exfoliated Ti 2 C, the methane capacity was supposed to be 28.8 wt% or 1148 V (STP)v -1 . Ti 2 C theoretically has much larger volume methane capacity than current methane storage materials, though its SSA is not very high.
By means ofin situintercalation polymerization Ti2CTx/EP nanocomposites were prepared, which possessed excellent mechanical and tribological properties.
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