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MXenes are the typical ions insertion-type two-dimensional (2D) nanomaterials, have attracted extensive attention in the Li

2D materials is a promising Na+ insertion-type material due to its unique layered structure, however, the long diffusion channels yielded by stacking limited the Na+ storage rate capability. Herein, a 3D MoS2–Ta4C3 heterostructure (M-Ta4C3) composite is designed by supported 2D MoS2 nanosheets on/in the surface/interlayers of 2D Ta4C3 matrix for achieving high rate Na+ storage. The 2D MoS2 nanosheets is confined in the interlayers of Ta4C3 matrix that can avoid the stacking and expand the interlayer spacing of Ta4C3 matrix, which enlarges the contact surface area between electrode and electrolyte, and exposes more electrochemical active sites for Na+ storage. The Ta4C3 matrix improves the conductivity, prevents the aggregation and confines the volume expansion of MoS2 nanosheets which optimizes the structure stability and provides short Na+ diffusion channels. The M-Ta4C3 exhibits a larger interlayer spacing of 1.69 nm, extraordinary electrochemical performance and outstanding rate capability which benefitted from the 3D heterostructure. The M-Ta4C3//AC SIC owns super energy and power densities of 87.6 Wh kg−1 and 3937.3 W kg−1. This work employs Ta4C3 MXene as a Na+ storage material for the first time, and it provides an idea to improve the Na+ storage performance of 2D materials by constructing a 3D heterostructure.

An ion insertion type in two-dimensional (2D) materials has attracted extensive attention making 2D materials as promising energy storage materials . However, the interlayer spacing plays a key role in the design of 2D materials with fast ions de-intercalation dynamics and high-rate capability. Here, an unprecedented and convenient organic molecular welding approach was proposed to controllably tune different interlayer spacings in Ti 3C2 MXene layers, resulting in pillar and strain- xDA-Ti3C2 structures by a dehydration condensation reaction between diacid molecules (HOOC(CH2)nCOOH) and -NH2 functionalized Ti3C2 layers. The xDA molecules can not only tighten the adjacent layers acting as ropes during the ion insertion process but also pillar the adjacent layers when ion extraction process was used to stabilize the Ti3C2 structure by suppressing the volume change. Furthermore, the interlayer spacing of xDA-Ti3C2 can be controllably tuned from 1.03 to 1.45 nm by choosing xDA with different lengths and controlled interlayer spacings of 1.35 and 1.38 nm can be achieved for the best rate capability of insertion/extraction processes with the superior diffusion coefficient of 4.6 × 10−7/2.8 × 10−8 cm2/s in Li+/Na+ batteries, respectively.

A facile method of chemical welding was proposed to construct the diamine molecules (xDM, x = 2, 3, 4, 6 and 8) pillared- and strained-graphene oxides (GO) with controllable interlayer spacing via the dehydration condensation reaction between GO and xDM. The interlayer spacing of xDM pillared- and strained-GO (GO-xDM) is controllably enlarged by choosing the length of xDM, which determines the pillaring effects. The GO-xDM exhibits a low diffusion barrier and ultrafast Li+ diffusion dynamics due to its enlarged interlayer spacing, which leads the excellent Li+ storage rate capability. The effects of interlayer spacing on Li+ diffusion dynamics are clarified that GO-2DM with the interlayer spacing of 0.911 nm displays the excellent Li+ storage performance and fast Li+ diffusion dynamics (DLi+=2.4 × 10−7 cm2 s−1). The GO-2DM presents a high capacity of 291.8 mAh g−1 at a current density of 0.1 A g−1 and a high-rate capability of 120.8 mAh g−1 at a current density of 5.0 A g−1. The GO-2DM//AC lithium-ion hybrid capacitor delivers a high energy density of 103.6 Wh kg−1 at a power density of 55.8 W kg−1, even reaches 2777.8 W kg−1 at a power density of 61.1 Wh kg−1. The approach of chemical welding provides a novel perspective for controllably enlarging interlayer spacing and designing two-dimensional (2D) energy storage materials with high-rate capability.

Sodium ion capacitors (SICs) have attracted considerable attentions since it is integrating the complementary features of both high energy and power densities. One of the most crucial tasks for develop highly efficient SICs is to increase the faradaic Na+ redox kinetics from the battery-type anode to match the electrical double-layer capacitance-type cathode. In this work, Mo2C nanoparticles uniformly anchored into cross-linked hierarchical porous carbon (HPC-Mo2C) have been produced by a water-soluble NaCl template strategy. The as-obtained HPC-Mo2C composite shows a large specific surface area of 385.6 m2 g−1 with well distributed micro–meso–macropores structure, delivering a superior rate capability (108.2 mAh g−1 at 5 A g−1) and robust long-term cycling of 190.6 mAh g−1 at 1 A g−1 after 2500 cycles. Electrochemical measurements illustrate that the Mo2C nanoparticles uniformly anchored into cross-linked hierarchical porous structure can accelerate fast Na+ diffusion kinetics toward excellent rate capacity and increase the pseudocapacitive behavior for the redox reaction. The SIC composed of HPC-Mo2C as anode and activated carbon (AC) as cathode delivers an impressive energy density of 130.2 Wh kg−1 and ultra-high power density of 30,000.0 W kg−1, as well as an unprecedented cycling stability of 88.9% retention after 10,000 cycles with a potential range of 0–4.0 V. This work may cater to the requirements for rationale kinetic matching electrode for the advanced SICs.

A three-dimensional hierarchical porous carbon loaded ultrafine Mo2C (3DHPC-Mo2C) nanomaterial was synthesized by an effective approach that combines NaCl template and K2CO3 in-situ activation together. The 3D hierarchical porous carbon with macro-meso-micropores interlacing structure acts as a skeleton provides a large surface area (409 m2 g−1) and effectively prevents the agglomeration of Mo2C during the carbonization process, which not only conducive to expose more active sites and shorten the transmission path of electrolyte ions but also helps to give full play to the features of Mo2C, such as high conductivity. Because of the outstanding microstructure, the 3DHPC-Mo2C shows a superior electrochemical performance that delivers a high specific capacitance of 206 F g−1 at 0.5 A g−1 and superior cycling stability of 96.6% through 7000 cycles. Meanwhile, an asymmetric supercapacitor (3DHPC-Mo2C//AC) was assembled in ionic liquid electrolyte (EMIMAC/AN) and achieves a high specific energy of 20 Wh Kg−1 at the specific power of 224 W Kg−1, which is higher than most reported carbide-based asymmetric supercapacitors and provide a promising strategy for the preparation of Mo2C and its application in energy storage.

MXenes are a new class of two-dimensional (2D) materials and have been considered as promising energy storage materials due to their high conductivity and unique layered structure. To improve the charge storage performance of these materials, it is crucial to prevent self-stacking and expand the interlayer spacing of MXenes since this will increase the transfer channels and accessible active sites for electrolyte ions and improve the dynamics of charge storage. This paper presents an effective approach to preventing self-stacking and expanding the interlayer spacing of Ti3C2 using electrostatic reassembly between lanthanum ions and exfoliated Ti3C2 sheets to obtain a secondary-formed multilayer-structured Ti3C2 (La/e-Ti3C2). An increased interlayer spacing and greater specific surface area were achieved and capacitive performance was improved compared with that of pure multilayer Ti3C2. The specific capacitance of La/e-Ti3C2 was found to be 233.3 F g−1 at a current density of 0.5 A g−1 and the capacitance retention under 2 A g−1 was as high as 94.3% after 10,000 cycles. An interesting result is presented, namely that a large interlayer spacing is beneficial for improving the rate capability of Ti3C2 at different current densities. The study paves the way for controllable tuning of the interlayer spacing, specific surface area, and pseudocapacitive performance of two-dimensional materials.

Transition metal dichalcogenides (TMDs) caused widespread concern because of their possess graphite-like two-dimensional structure, which allows Na+ reversible de-intercalation between the interlayers and contributes high theoretical capacity. However, the poor conductivity and structural instability greatly limited their application to sodium ion batteries (SIBs). Herein, three-dimensional (3D) honeycomb MoSe2/rGO nanocomposites with outstanding sodium ion storage performance were prepared. The MoSe2/rGO combined the advantages of MoSe2 and rGO. The typical layered structure of MoSe2 provide Na+ diffusion pathways and sufficient active sites, while the rGO increase conductivity and alleviate structural change during Na+ insertion/extraction process. The stable discharge capacity of MoSe2/rGO reaches 300 mAh g−1 at 0.1 A g−1 and retains 247 mAh g−1 after 100 times. It retains a high capacity of 214.7 mAh g−1 at 1 A g−1 and shows outstanding rate capability. The MoSe2/rGO//AC hybrid sodium-ion capacitors (HSIC) achieves a high capacitance of 56.7 F g−1 at 0.1 A g−1, it exhibits an energy density of 87.7 W kg−1 at a power density of 208.8 W h kg−1 and retains 50.5 W h kg−1 when it increases to 1051.4 W kg−1. The article brings up a novel opinion for designing porous TMDs based composites as ideal energy storage materials.

Iodine-catalyzed three component reaction of quinazoline-2,5-diones, aldehydes, and styrenes provides allylamine derivatives was described. Both paraformaldehyde and ethyl glyoxalate can be applied in this reaction with simple styrenes with high regioselectivity.

Growth differentiation factor 9 (GDF9) is expressed in oocytes and is thought to be required for ovarian folliculogenesis. Given this function, GDF9 may be considered as a candidate gene controlling pig ovulate rate. In this study, the complete coding sequence was cloned (encoding a 444 amino acid), intron sequence and partial 5' -UTR of pig GDF9. RT-PCR results showed that GDF9 mRNA is expressed in a wide range of tissues of the ruttish Erhualian pig. The expression levels of GDF9 mRNA in pituitary, ovary, uterus and oviduct are higher in the Erhualian pigs than those in Duroc pigs, especially in pituitary with a significant difference (P < 0.05). Comparative sequencing revealed 12 polymorphisms, including 8 single nucleotide polymorphisms (SNPs) and one 314 bp indel in noncoding regions, and the other 3 SNPs in coding regions. Four polymorphisms, G359C, C1801T, T1806C and 314 bp indel, were developed as markers for further use in population variation and association studies. The G359C polymorphism segregates only in Chinese native pigs, Erhualian and Dahuabai, on the contrary, 314 bp indel segregates only in Duroc and Landrace. C1801T and T1806C sites seem to be completely linked and segregate in Erhualian, Dahuabai and Landrace. In a word, GDF9 may be not associated with pig litter size in extensive populations as per the studies of allele distributions of the four polymorphisms and pilot association in four breeds.