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MXene is a new family of two-dimensional transition metal carbides or carbonitrides with graphene-like 2D morphology. The chemical formula of MXene is M n+1 X n T z , where M is an early transition metal, X is C and/or N, T stands for surface-terminating functional groups like F-, OH-, O 2-, etc., and n = 1, 2, or 3. It can be achieved by selective etching of the A element from the MAX phases, and HF is an etchant mostly used. First-principles calculations about MXene have been performed to reveal the structure and properties. MXene has also been found to have a unique two-dimensional layered structure, large specific surface area and good electrical conductivity, stability, magnetic and mechanical properties, and thus it is promising in many fields, including energy storage, catalysis and adsorption. This article reviews the quite recent progress of MXene based on theoretical and experimental considerations, especially its structure, synthesis, and applications. Finally, the suggestions about existing challenges and future developments are proposed. MXene is expected to be used for more various applications with further extensive research.

To improve the layer spacing and the electrocatalytic performance of Ti 3 C 2 , the carbon nanotubes (CNTs) was utilized to tailor the microstructure. Layered Ti 3 C 2 , obtained by etching Ti 3 AlC 2 with HF, hydroxylated carbon nanotubes (CNTs) and potassium tetrachloropalladate (K 2 PdCl 4) were used to synthesize Pd naoparticles supported on Ti 3 C 2-CNT (Pd/Ti 3 C 2-CNT) catalyst through ultrasonic dispersion and solvothermal method. XRD, FE-SEM and XPS were adopted to investigate the effect of CNT on the microstructural tailoring of Ti 3 C 2 interlayers. The electrocatalytic performance of Pd/ Ti 3 C 2-CNT catalysts for both formic acid and methanol in acidic and alkaline solutions, were investigated by cyclic voltammetry, chronoamperometry, and AC impedance spectroscopy, respectively. The results validated that the intercalation of CNTs into Ti 3 C 2 interlayers, whose "bridge" effects benefit the electron transportation in the catalysts, and thus the electrocatalytic performance of Pd/Ti 3 C 2-CNT was elevated.

Pt、Ru 配比的 PtRu/(Ti 3 C 2 T x) 0.5-(MWCNTs) 0.5 阳极催化剂材料, HF 腐蚀 Ti 3 AlC 2 得到 Ti 3 C 2 T x , 与酸化处理的多壁碳纳米管(MWCNTs)复合后通过溶剂热法负载 Pt、 Ru 颗粒。 通过 XRD、 SEM、 EDS、 TEM、 XPS 等分析铂钌的协同关系。结果表明: Ru 原子与 Pt 原子晶格混合, 形成了粒径约 3.6 nm 的铂钌双金属合金。电化 学分析结果表明: Pt 1 Ru 0.5 /(Ti 3 C 2 T x) 0.5-(MWCNTs) 0.5 催化剂具有最佳的电化学性能, 其电化学活性面积(Electrochemical Active Area, ECSA)为 139.5 m 2 /g, 正向峰电流密度为 36.4 mA/cm 2 。

Carbon nanotubes (CNTs)-dispersed ceramics were usually obtained by simple mixing, or firstly dispersing the metal catalysts inside ceramic powders, and then growing CNTs from the thermal decomposition of hydrocarbon gas. In the present study, a novel route for the fabrication of Al 2 O 3 NiCNTs nanocomposites was proposed by co-precipitation of CNTs and Ni nanoparticle on Al 2 O 3 powder using nickelocene as a precursor in a rotary CVD reactor. Fine Ni nanoparticles (1050 nm in diameter) and CNTs (2050 nm in diameter and as long as 1¯m in length) were uniformly dispersed on agitated Al 2 O 3 powders. After spark plasma sintering at 1923 K for 0.6 ks, the Al 2 O 3 NiCNTs nanocomposites showed uniform microstructure and enhanced mechanical properties. Carbon incorporated in nickel changed from amorphous to crystalline phase state after the high temperature treatment. No other impurities were identified, and the incorporation of CNTs and Ni was also found to enhance the relative density and mechanical properties of Al 2 O 3 . Thus the present method is promising for fabrication of high performance CNTs-ceramic composites.