Latest ArticlesThe rational design and construction of heterojunction structure is an effective strategy to improve the photocatalytic performance. Herein, a series of BiOBr nanosheets-immobilized TiO2/Ti3C2Tx MXene hybrid materials with heterojunction structure were synthesized by a facial one-step hydrothermal method. The ternary composites show outstanding performance as photocatalysts for the degradation of rhodamine B due to the optimized synergetic effects of BiOBr, TiO2 and Ti3C2Tx. The improved photocatalytic performance is remarkably attributed to the construction of a heterojunction between TiO2 and BiOBr due to their well-matching of energy band position, which can enhance the absorption for visible light and promote the transfer of photo-generated charge carriers. Moreover, Ti3C2Tx acts as an electron trap to further accelerate the separation of photo-generated electrons and holes.
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.
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.
Ti3C2 belongs to MXenes family, which is a new two-dimensional material and has been applied in many fields. With simple method of hydrothermal and high temperature calcination, nanostructured Ni/Ti3C2Tx hybrid was synthesized. The stable layer structure of Ti3C2 MXene providing high surface area as well as excellent electronic conductivity are beneficial for deposition and decomposition of discharge product Li2O2. Furthermore, possessing special catalytic activity, Ni nanoparticles with size of about 20 nm could accelerate Li2O2 breaking down. Taking advantage of two kinds of materials, Ni/Ti3C2Tx hybrid as cathode of Li-O2 battery can achieve a maximal specific capacity of 20, 264 mAh/g in 100 mA/g and 10, 699 mAh/g in 500 mA/g at the first cycle. This work confirms that the prepared Ni/Ti3C2Tx hybrid exhibiting better cycling stability points out a new guideline to improve the electrochemical performance of lithium-oxygen batteries.
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.
The problem of water pollution has become increasingly serious, and it has already threatened the survival of mankind and has become an obstacle to the healthy development of human health. Here, we prepared a novel polyvinyl alcohol (PVA)/polyacrylic acid (PAA)/MXene fiber membrane by electrospinning. After heat treatment of film and subsequent modification with Pd nanoparticles, PVA/PAA/MXene@PdNPs composite nanofiber membrane with high specific surface area and excellent catalytic performance was finally prepared. The uniform distribution of MXene sheets in the composite fiber membrane not only solves the problem that the MXene sheet is not easy to be monolayerized, but also can grow the self-reduced Pd nanoparticles on the MXene sheets. In addition, the composite nanofiber membrane exhibits excellent catalytic ability and cycle stability for 4-nitrophenol (4-NP) and 2-nitrophenol (2-NA), providing new strategy for the study of catalytic composite materials related to degradation of wastewater.
Two-dimensional (2D) Ti3C2Tx MXene is an attractive additive not only used in base oil due to its low friction coefficient, but also used in composites due to its high aspect ratio and rich surface functional groups. So far there has been intense research into polymer matrix composites reinforced with Ti3C2Tx. Here we report on the use of 2D Ti3C2Tx to enhance the mechanical and frictional properties of Al matrix composites. Ti3C2Tx/Al composites were designed and prepared by pressureless sintering followed by hot extrusion technique. The prepared composites exhibit a homogeneous distribution of Ti3C2Tx. The Vickers hardness and the tensile strength continuously increase with increasing Ti3C2Tx content. A hardness of 0.52 GPa and a tensile strength of 148 MPa were achieved in the 3 wt% Ti3C2Tx/Al composite. The frictional properties of pure Al and the Ti3C2Tx/Al composite were comparably studied under dry sliding. A low friction coefficient of 0.2, twice lower than that of pure Al, was achieved in the 3 wt% Ti3C2Tx/Al composite. Ti3C2Tx acting as a solid lubricant reduces the abrasive wear in the composite, improving the frictional properties of Al matrix composites.
Two-dimensional transition-metal carbide materials, or MXenes, have attracted great attention in energy-related fields due to their excellent electrical conductivity, and large interlayer spacing. In this work, a simple method involving combustion synthesis and acid treatment to prepare accordion-like Ti3C2Tx MXene with open structure and high crystallinity, which is employed as anode materials in lithium-ion capacitors. Due to the improved ion diffusion and electron transportation of Ti3C2Tx anode, the mismatched electrode kinetics can be largely alleviated to acquire an enhanced power performance. The assembled Ti3C2Tx-based lithium-ion capacitors provides a maximum energy density of 106 Wh/kg and still exhibits a superior energy density of 79 Wh/kg even at a higher power density of 5.2 kW/kg, which provides a new platform for MXene materials with porous and crystalline features toward both high energy and power densities.
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.
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