Latest ArticlesThe development of efficient method to prepare poly(silyl ether)s (PSEs) is highly desirable. Herein, an environmentally sustainable copper-catalyzed dehydrocoupling polymerization was developed with good yields and high molecular weight (up to 48, 400 of Mn and up to 97% yield). Monomers of different types (AB type or AA and BB type) are suitable to afford PSEs. The PSEs show good thermal stability and low glass-transition temperature.
Cationic polymers, also known as polycations, are considered to be the most potential non-viral gene carriers due to their unique advantages such as the ability to bind the negative charge of nucleic acid molecules. Multicomponent polymerization (MCP) is a one-step, tandem strategy to construct complex structures based on multicomponent reactions. Herein, we developed a metal-free MCP method based on three monomers of p-dinitrovinylbenzene (p-DNVB), 1, 1-dimethylethyl N, N-dibromocarbamate (BocNBr2), and bis-secondary-amines with a ratio of 1:2:1, to access a library of Boc-substituted polyamidines with well-defined structures and suitable molecular weights (Mw ranging from 4400 Da to 11, 000 Da) in high yields (up to 85%) under mild conditions. Upon the removal of Boc groups, a series of water-soluble polymers with cationic property were prepared and their gene binding capability was further evaluated.
Aqueous rechargeable Ni−Zn batteries are considered as a new generation of safe and reliable electrochemical energy storage system. However, low electronic conductivity of Ni-based cathodes hinders the practical application of Ni-Zn batteries. This problem can be overcome by compositing the Ni-based cathode with highly conductive carbon substrates. A chemical oxidation pre-treatment is popularly applied to the carbon substrates to increase their hydrophilicity and thus facilitate the growth of active materials in aqueous systems. However, the anodic stability of the oxidized carbon substrates is greatly challenged, which has never been addressed in previous reports. In this work, we first compared the anodic stability of carbon fiber paper with and without oxidation treatment and find that carbon substrate with the chemical treatment caused remarkable oxidization current in the required voltage range. To take both anodic stability and fine growth of active materials into account, here we demonstrated a facile physical surface-treatment method of ethanol wetting to replace the chemical treatment. The ethanol infiltration removes gas adsorption on carbon substrates and thus promotes their hydrophilicity. This cost-effective strategy simultaneously achieves a high anodic stability and a fine growth and uniform distribution of nickel-cobalt hydroxide on the carbon microfibers. The resulting Ni-Zn battery provides a high discharge capacity of 219 mAh/g with an operation cell voltage of 1.75 V.
Aqueous zinc anodes have attracted the attention of many researchers owing to their high safety, low cost, and high theoretical specific capacity. However, its practical application is severely limited by the dendrite growth on zinc anode. Herein, we develop an intrinsically zincophobic barium-titanate protective layer with a porous structure to suppress the zinc dendrite formation by homogenizing the ion distribution on the anode surface, increasing the nucleation sites, and limiting the irregular zinc growth. Based on these synergistic effects, the coated zinc anode can exhibit long cycle life (840 h at 0.5 mA/cm2 for 0.5 mAh/cm2) and low voltage hysteresis (36 mV). This work can provide a feasible direction for the design of intrinsically zincophobic coating materials to uniformize the zinc stripping and plating.
Applying mixed oxygen ionic and electronic conducting (MIEC) oxides as the cathode offers a promising solution to enhance the performance of solid oxide fuel cells (SOFCs). However, the phase instability in CO2-containing air and sluggish oxygen reduction activity of MIEC cathodes remain a long-term challenge for optimizing the electrochemical performance of SOFCs. Herein, a heterovalent co-doping strategy is proposed to enhance the oxygen reduction activity and CO2 tolerance of SOFCs cathodes, which can be demonstrated by developing a novel BaCo0.6Fe0.4O3-δ (BCF)-based MIEC oxide, BaCo0.6Fe0.2Sn0.1Y0.1O3-δ (BCFSY). In addition to improving the stability of BCF-based perovskites, this strategy achieves an optimized balance of ionic mobility and oxygen vacancies due to the synergies between the effects of the co-dopants. Compared with single-doped materials, BCFSY exhibits improved CO2 tolerance and considerably higher ORR activity, which is reflected in a significantly lower polarization resistance of 0.15 Ω cm2 at 600 ℃. The results of this work provide an efficient tactic for designing electrode materials for SOFCs.
Zinc-ion batteries (ZIBs), in particular quasi-solid-state ZIBs, occupy a crucial position in the field of energy storage devices owing to the superiorities of abundant zinc reserve, low cost, high safety and high theoretical capacity of zinc anode. However, as divalent Zn2+ ions experience strong electrostatic interactions when intercalating into the cathode materials, which poses challenges to the structural stability and higher demand in Zn2+ ions diffusion kinetics of the cathode materials. Here, a microwave-assisted hydrothermal method is adopted to prepare pre-potassiated hydrated vanadium pentoxide (K0.52V2O5·0.29H2O, abbreviated as KHVO) cathode material, in which the potassium ions pre-inserted into the interlayers can act as "pillars" to stabilize the lamellar structure, and crystal water can act as "lubricant" to improve the diffusion efficiency of Zn2+ ions. Consequently, the KHVO displays high electrochemical properties with high capacity (~300 mAh/g), superior rate capability (69 mAh/g at 5 A/g) and ultralong cycling performance (> 1500 cycles at 2 A/g) in quasi-solid-state ZIBs. These superior Zn storage properties result from the large diffusion coefficient and highly stable and reversible Zn2+ (de)intercalation reaction of KHVO.
Developing transition metal oxides (TMOs) with high energy, power, and long cycle lifetime for electric energy storage devices remains a critical challenge to date. Herein, we demonstrate a facile method that enables in-situ transformation of nickel cobalt oxide nanowire arrays (NiCoO NWA) into hierarchical nanowire-nanosheet arrays (ac-NiCoO NWSA) for enhanced energy storage properties. More specifically, the method leads to formation of atomically thin nanosheets (only 2.0 nm) and creates abundant antisite defects and oxygen vacancies. Owing to these merits, the as-prepared ac-NiCoO NWSA electrode exhibits over five-fold higher specific capacity, superior rate capability (up to 100 A/g), and excellent cycling stability of 10, 000 cycles at 50 A/g in alkaline electrolyte compared to pristine NiCoO NWA. Density functional theory (DFT) simulations elucidate the electrochemical activity enhancement mechanism of the TMOs. Moreover, our method triggers similar structural reconstruction phenomenon on other TMOs including ZnCo-, CoMn- and ZnNiCo-oxides, proving the universality of the method. Our findings provide a general method towards simultaneously manipulating the micro-morphologies and defects of TMOs for advanced energy storage devices.
The high effective nano-hybrid pour point depressant (PPD) has attracted extensive attention for its potential application in improving the cold flow properties of diesel fuel. In this paper, the nano-hybrid PPD was prepared by melt-blending method using three different alkyl chain lengths (i.e., tetradecyl, hexadecyl, and octodecyl) of n-alkyl methacrylate-maleic anhydride copolymers (R1MC-MA, R1 = C14, C16, C18) and SiO2 nanoparticles. The effect of those nano-hybrid PPDs on the cold filter plugging point (CFPP) and solidifying point (SP) depressing of diesel fuel were studied. Results indicated that nano-hybrid PPD showed much better performance on diesel fuel. The diesel fuel treated with 0.2 wt% C14MC-MA/SiO2 nano-hybrid PPD exhibited the best depression in CFPP and SP by 6 ℃ and 18 ℃, respectively, which higher than that of single C14MC-MA. Viscosity-temperature curves and polarized optical microscopy were conducted to explore the performance mechanism; and results presented that nano-hybrid PPD of C14MC-MA/SiO2 could effectively lower the low-temperature viscosity, and modify the crystallization behavior and crystal morphology of diesel. Therefore, the cold flow properties of diesel were significantly improved.
A facile fabrication strategy is reported to obtain N/O codoped porous carbon nanosheets for purpose of ameliorating the charge transfer and accumulation in the concentrated LiTFSI (lithium bis(trifluoromethane sulfonyl)imide) electrolyte. By tunning the feed ratio of comonomers, the porous nanosheet structure is endowed with a significant ion-adsorption surface area (1630 m2/g) and interconnected hierarchical porosity; meanwhile, high-level N/O dopants (N: 3.58 at%, O: 12.91 at%) increase the effective contact area for electrolyte ions, and further facilitate rapid ion/electron transfer. Benefiting from the advantageous features, carbon nanosheets electrode reveal an enhanced specific capacitance (375 F/g) in three-electrode configuration and the H2SO4-based device yields a high gravimetric energy density of 11.4 Wh/kg. Particularly, the ion-diffusion highways in porous carbon nanosheets contribute to the 2.25 V LiTFSI-based symmetric device with a high energy delivery up to 33.1 Wh/kg. This work offers an inspiring strategy for facile fabrication of carbon nanosheets, and demonstrates their promising application in "water-in-salt" electrolyte-based supercapacitor systems.
Alcohol fuels oxidation plays a significant role in carbon sustainable cycling and high-performance catalyst with a strong anti-poisoning effect is desired. Herein, Pt-Ni alloy supported on the N-doped graphene aerogel synthesized by simple freeze-drying and annealing was demonstrated to have such catalytic ability for alcohol fuel oxidation. Pt-Ni alloy particles were found uniformly dispersed over the surface of 3D N-doped graphene aerogel. High anti-poisoning ability for CO-like intermediates oxidation was demonstrated by the CO-stripping experiment. The as-prepared catalyst was found to have outstanding catalytic performance for methanol and ethanol oxidation with high catalytic activity, stability and catalytic kinetics. Compared to the control samples, the improved catalytic ability could be due to the presence of oxophilic Ni species and the support effect of 3D N-doped graphene aerogel that combined multi-advantages of large surface area, facile mass transfer, and abundant defects.
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