Latest ArticlesHerein, a simple yet efficient hydrothermal strategy is developed to in-situ convert multi-layered niobium-based MXene (Nb2CTx) to hierarchical Nb2CTx/Nb2O5 composite. In the hybrid, the Nb2O5 nanorods are well dispersed in and/or on the Nb2CTx. Thanks to the synergetic contributions from the high capacity of Nb2O5 and superb electrical conductivity of the two-dimensional Nb2CTx itself, the resultant Nb2CTx/Nb2O5 hybrid exhibits excellent rate behaviors and stable long-term cycling behaviors, when evaluated as anodes for Li-ion batteries.
Ti3CNTx MXenes with unique electrical conductivity can be widely applied for supercapacitors and electromagnetic shielding. However, its relatively low-yield quaternary nitrogen-containing Ti3AlCN ceramics precursor (less than 50%), due to the inevitable Al segregation during the synthesizing process, significantly hindered its widely commercial applications. Herein, we employed the controllable AlNoversaturation precursor strategy to precisely tune the phase transition point of quaternary Ti3AlCN ceramics to obtain high-yield Ti3AlCN precursor for the purpose of high conductivity Ti3CNTx MXenes. Combined energy dispersive X-ray spectrometer (XRD) with X-ray photoelectron spectroscopy (XPS) characterizations, the yield of the quaternary nitrogen-containing Ti3AlCN ceramics was evidently proved to be up to 70%, which is 1.4 times than that of previously reported works. Such relatively highyield quaternary Ti3AlCN is mainly ascribed to the elimination of Al segregation. Based on it, we further developed accordion-like two-dimensional (2D) MXene via hydrofluoric acid etch and vacuum freezedry. This novel accordion-like 2D Ti3CNTx MXene possesses high electrochemical capacitive properties (209 F/g). Therefore, this controllable AlN-oversaturation precursor strategy will pave a way to exploit costly high-yield MAX ceramics precursor for high conductivity MXenes and also play a powerful role in promoting their practical applications including electrical and magnetic engineering fields.
The development of two-dimensional hybrid nanomaterial derived from MXenes as high performance electrode material is the key component for the advanced energy storage and conversion systems. In the past decades, MXene derived nanomaterials have attracted greatly interest in scientific activity and potential applications because of their unique synergistic properties such as high thermal stability, excellent electrical conductivity, large surface area, easy to handle and outstanding electro and photo chemical properties. This review is focused on the synthesis of hybrid nanomaterials from MXene (Ti3C2Tx) for renewable energy conversion and storage application including hydrogen evolution reaction, supercapacitor, lithium-ion batteries and photocatalysis. Finally, we also summarized the prospect and opportunities of novel two-dimensional hybrid nanomaterials derived MXene (Ti3C2Tx) for futuristic sustainable energy technology
Ti3C2Tx has been emerging as an attractive platform to prepare composite catalysts, and their assembly into integrated catalytic materials represents a key step forward toward practical applications. However, the swelling behavior of Ti3C2Tx leads to significant structure change, which challenges the stability of Ti3C2Tx-based integrated functional materials for catalytic applications. Here we report a facile synthesis of Pd/Ti3C2Tx⊂graphene hydrogels in which Pd/Ti3C2Tx are spatially encapsulated in the 3D porous graphene framework. The porous interconnected structure not only affords efficient mass transfer and desirable functional accessibility to catalytic active sites, but also effectively buffers the swelling behavior of Ti3C2Tx. When applied for catalytic hydrogenation of nitroaromatic compounds, the mechanically robust Pd/Ti3C2Tx⊂graphene hydrogels exhibit efficient activities, easy separability, and good cyclability. This work is expected to promote the application of Ti3C2Tx-based functional materials for practical applications involving interactions with salt solutions, such as supercapacitors, catalysis, and water purification.
MXene-based electrode materials exhibit favorable supercapacitor performance in sulfuric acid due to praised pseudocapacitance charge storage mechanism. However, self-stacking of conventional MXene electrodes severely restricts their electrochemical performance, especially at high loading. Herein, a flexible cross-linked porous Ti3C2Tx-MXene-reduced graphene oxide (Ti3C2Tx-RGO) film is skillfully designed and synthesized by microscopic explosion of graphene oxide (GO) at sudden high temperature. The generated chamber structure between layers could hold a few of electrolyte, leading to a close-fitting reaction at interlayer and avoiding complex ions transmission paths. The Ti3C2Tx-RGO film displayed a preferable rate performance than that of pure Ti3C2Tx film and a high capacitance of 505 F/g at 2 mV/s. Furthermore, the uniform intralayer structure and unique energy storage process lead to thickness-independenct electrochemical performances. This work provides a simple and feasible improvement approach for the design of MXene-based electrodes, which can be spread other electrochemical systems limited by ions transport, such as metal ions batteries and catalysis.
MXenes, the new family of two-dimensional (2D) transition metal carbides/nitrides, can serve as the substrate materials for the catalysts due to the large specific surface area, tunable electronic structures and thermal stability. The first 2D layered MXene, Ti3C2, was successfully obtained by selective etching of the A element from the MAX phases using hydrofluoric acid (HF) at room temperature in 2011. In this review, we summarize the preparation, structure of MXenes and discuss the recent progress in potential application of MXenes in catalysis, mainly in CO oxidation and oxygen reduction reaction (ORR), from the views of both experimental and theoretical investigations. The outlook of the major challenges and future directions on research of MXenes is also included.
Electrochemical reduction of N2, as an eco-friendly alternative, not only allows the use of protons in water as a source of hydrogen under mild conditions but also can be driven by renewable electric energy. The major challenge is to identify high-efficiency electrocatalysts. MXene is a new class of 2D transition metal carbides, nitrides, and carbonitrides that have received significant attention in electrocatalysis. The investigations on MXene in electrocatalytic nitrogen fixation are rapidly proceeding, and some breakthroughs have emerged very recently due to MXenes' satisfactory catalytic activity. Here, the recent progress concerning the MXene-based catalysts for electrochemical N2 reduction reaction (NRR) is highlighted. In regards to giving guidelines for exploring more efficient MXene-based catalysts for the NRR, the fabrication and surface modification of MXene are discussed. Besides, the shortcomings and challenges of current research are summarized and the future research directions are prospected.
Available onlineSilicon monoxide (SiO) is a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity (~2400 mAh/g), low working potential (< 0.5 V vs. Li+/Li), low cost, easy synthesis, nontoxicity, abundant natural source and smaller volume expansion than Si. However, low intrinsic electrical conductivity, low initial Coulombic efficiency (ICE) and inevitable volume expansion (~200%) impede its practical application. Here we fabricate SiO/wrinkled MXene composite (SiO-WM) by an electrostatic self-assembly method. Importantly, this method is simple, scalable and taking into account all the issues of SiO. As a result, the SiO-WM exhibits improved rate capability, cycling performance and ICE than bare SiO.
Designing efficient electrocatalysts with low Pt loadings for hydrogen evolution reaction (HER) is urgently required for renewable and sustainable energy conversion. Here, we report a strategy that Pt nanoparticulates are spontaneously immobilized on porous MXene/MAX monolith as HER catalysts by utilizing the redox reaction between Ti3C2Tx MXene and [PtCl4]2- in H2PtCl6 aqueous solution. By taking advantage of homogeneously distributed Pt nanoparticulates on highly electrically conductive porous Ti3C2Tx/Ti3AlC2 monolith, the as-prepared electrocatalysts show high catalytic performance for hydrogen evolution. Specifically, the binder-free electrocatalysts have Pt loadings as low as 8.9 μg/cm2, with low overpotential of 43 mV at a current density of 10 mA/cm2 and low Tafel slope that three times lower than porous Ti3C2Tx/Ti3AlC2 without Pt loading. This strategy offers a new approach to constructing ultra-low Pt-loading HER catalysts on the basis of in situ redox reaction between noble metal ions and MXenes.
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