Latest ArticlesSurface engineering that could modulate the surface shape to be endowed with the high specific surface ratio, abundant chemical dangling bonds and improved defects exposure is highly desired and needs further exploring. Here, we report a facile strategy of surface engineering on decorating the controllable segmented copper-iron nanowires arrays (Cu-Fe NWs) with their respective hydroxides. Specifically, the pristine segmented Cu-Fe NWs are firstly synthesized via sequentially electrodepositing Cu NWs and Fe NWs inside the nanochannels of anode aluminum oxide (AAO) template. Subsequently, the surface and interface of Cu-Fe NWs are wet-chemically etched, in which the metallic Cu and Fe are partially converted into Cu(OH)x nano-fibrous roots (NFRs) and FeO(OH)y nanoparticles (NPs), and finally decorate around the respective outer-surface of Cu NWs and Fe NWs segments. As one case of the applications in hydrogen evolution reaction (HER), our surface-modified Cu-Fe NWs exhibit improved catalytic activity compared with Fe NWs.
At present, replacing the liquid electrolyte in a lithium metal battery with a solid electrolyte is considered to be one of the most powerful strategies to avoid potential safety hazards. Composite solid electrolytes (CPEs) have excellent ionic conductivity and flexibility owing to the combination of functional inorganic materials and polymer solid electrolytes (SPEs). Nevertheless, the ionic conductivity of CPEs is still lower than those of commercial liquid electrolytes, so the development of high-performance CPEs has important practical significance. Herein, a novel fast lithium-ion conductor material LiTa2PO8 was first filled into poly(ethylene oxide) (PEO)-based SPE, and the optimal ionic conductivity was achieved by filling different concentrations (the ionic conductivity is 4.61 × 10−4 S/cm with a filling content of 15 wt% at 60 ℃). The enhancement in ionic conductivity is due to the improvement of PEO chain movement and the promotion of LiTFSI dissociation by LiTa2PO8. In addition, LiTa2PO8 also takes the key in enhancing the mechanical strength and thermal stability of CPEs. The assembled LiFePO4 solid-state lithium metal battery displays better rate performance (the specific capacities are as high as 157.3, 152, 142.6, 105 and 53.1 mAh/g under 0.1, 0.2, 0.5, 1 and 2 C at 60 ℃, respectively) and higher cycle performance (the capacity retention rate is 86.5% after 200 cycles at 0.5 C and 60 ℃). This research demonstrates the feasibility of LiTa2PO8 as a filler to improve the performance of CPEs, which may provide a fresh platform for developing more advanced solid-state electrolytes.
Rational construction of fine-tuning and precisely controllable topological nanostructures based on supramolecular self-assembly system remains a challenge. Herein, coumarin-12-crown-4 (1) as a building block was synthesized by one-pot method and showed reversible high stereo-selective photodimerization (anti-head-to-head dimer (anti-HH-1): syn-head-to-head dimer (syn-HH-1) = 10.8:1) and photocleavage. Helical nanobelts were formed by the self-assembly of 1 through asymmetrical H-bonds, which were in concordance with the crystal state superstructure. Upon irradiation with 365 nm light, these nanobelts transformed into nanoballs which were constructed by three building blocks. Further, we investigated the photoreaction of 1 and got two pure covalent dimers (anti-HH-1 and syn-HH-1). The anti-HH-1 self-assembled into hollow micro-vesicles. The transformation of superstructures based on photo-controlled multiple blocks shines a light to the research on the relationship between molecules and superstructures.
Dielectric elastomers (DEs) have drawn much attention owing to their application prospects in artificial muscles and soft robotics, it is still a big challenge to prepare DEs with high electromechanical performances. This work reports a highly stretchable poly(thioether)-b-polysiloxane-b-poly(thioether) triblock copolymer based homogenous DEs with high electromechanical properties. The triblock copolymer (PSiPGE) was synthesized through the ring-opening polymerization (ROP) of phenyl glycidyl ether (PGE) and carbonyl sulfide (COS) catalyzed by silicon alkoxides. The dipoles (benzene rings) on the side groups of PSiPGE improved the dipole polarizations and the phase separation structure of this triblock copolymer enhanced the interfacial polarizations between poly(thioether) and polysiloxane, and thus improving the dielectric constant (ε', up to 5.8). In addition, the PSiPGE exhibited low elastic modulus (Y, 0.04 MPa), and thus possessed high electromechanical sensitivity (β, ~145 MPa−1) which is much higher than that of most homogenous DEs. This work provides a new strategy to construct homogenous DEs with excellent electromechanical performances, leading to a greater application aspect in the actuated devices.
Constructing molecule@support composites is an attractive strategy to realize heterogeneous molecular electrocatalysis. Herein, we synthesized metal-organic framework (MOF)-supported molecular catalysts for hydrogen evolution and oxygen reduction reaction (HER/ORR). Ligand exchange strategy was used to prepare molecule@support hybrids due to the same functional group. A series of hybrids were obtained using Co porphyrin (1) and different MOFs including MIL-88(Fe), MOF-5(NiCo) and UIO-66(Zr). The 1@MOF-5(NiCo) had the best HER and ORR activity compared with 1@MIL-88(Fe) and 1@MOF-5(NiCo). These hybrids also exhibited tunable selectivity for ORR with four-electron process, which can be attributed to the synergistic effect of porphyrin molecules and MOFs. This work provides a possibility for molecular catalysts to improve activity of HER and tune selectivity of ORR.
Developing efficient and inexpensive OER electrocatalysts is a challenge for overall water splitting. Herein, the heterostructured FeCo LDH@NiCoP/NF nanowire arrays with high performance were rationally designed and prepared using an interface engineering strategy. Benefitting from the special heterostructure between FeCo LDH and NiCoP, the as-synthesized FeCo LDH@NiCoP/NF electrocatalyst exhibits outstanding OER performance with an exceptionally low overpotential of 206 mV to achieve 20 mA/cm2 current density in an alkaline electrolyte. Importantly, a cell constructed using the FeCo LDH@NiCoP/NF electrocatalyst as cathode and anode just needs a voltage of 1.48 V at 10 mA/cm2, and shows excellent stability over 80 h. Experimental and theoretical results verified that the introduction of NiCoP efficiently regulates the electronic structure of FeCo LDH, which tremendously boosts the conductivity and intrinsic catalytic activity of FeCo LDH@NiCoP/NF electrocatalyst. The present work provides guidance for the preparation of other efficient and cheap electrocatalytic materials.
A novel type sandwich-like composite films composed of ZIF-8 and CdTe QDs were successfully constructed through facile layer-by-layer assembly strategy and their potential applications were also explored. Based on the limitation effects of the aperture of ZIF-8, CdTe QDs/ZIF-8 fluorescent composite films exhibit obvious selective optical response toward hydrogen peroxide and folic acid. Furthermore, tunable colorful light emission composite films in the red-green region are obtained through incorporating two different sized QDs and ZIF-8 films into one composite films.
Enterocytozoon hepatopenaei (EHP) infection has seriously affected prawn culture globally. The symptoms of the infection are not apparent, and traditional detection methods are time consuming and low in accuracy. We developed a new onsite rapid testing device (size 18.8 × 16.7 × 6.6 cm3) for EHP based on magnesium pyrophosphate precipitation and facilitated by loop mediated isothermal amplification (LAMP). The design and fabrication of the device enables efficient light absorbance. The device has a highly sensitive detector, high-precision thermal controller, and humanized touch screen. The temperature control precision of the device is 0.2–0.3 ℃ at 60 ℃, 63 ℃, and 65 ℃. The coefficients of variation values (CVV) of the luminous power in one channel at light on and off were found to be 0.0097 and 0.0014, respectively, within 1 h. The CVV of the background, luminous power, and values of eight PCR tubes filled with pure water were all less than 5%. In the EHP experiment, eight samples (including seven positive and one negative) confirmed the effectiveness of the device, and four positive and four negative samples verified whether cross-contamination exists. Among them, the rise time of the curve was about 15 min. These results assert that the developed device exhibits enhanced stability and uniformity and has excellent performance with high sensitivity, good specificity, and low testing time. Moreover, the optimal and minimum absorbance range was 555–655 nm for monitoring the production of LAMP.
A hydrogen fluoride-free and chloro-free method for synthesizing LiPF6 was developed. Employing CaF2 as the direct fluorinating reagent instead of hydrogen fluoride made it much safer and more environment-friendly than conventional methods and reduced the metal residues in product owing to the relatively low-acid reaction conditions less corrosive to equipments. The use of P2O5 as phosphorus source instead of traditionally employed PCl5 significantly reduced the chloro residue in product. Ca(H2PO4)2, the only by-product of the process, could be easily converted into Ca3(PO4)2, a best-selling chemical. The above advantages not only reduce the production costs by ca. 20%, but also significantly improve the product purity. The fluorine-oxygen exchange reaction is a completely new technique for LiPF6 production and may bring about technological revolution in the related industry.
Electrocatalytic oxygen evolution reaction (OER) is one of the important half reactions of electrocatalytic water splitting. However, the slow kinetic process involving four-electron transfer severely limits its reaction efficiency, which in turn limits the overall electrocatalytic hydrolysis efficiency. In order to improve the activity of the electrocatalytic OER, researchers mainly update the catalyst from three aspects, that is, increase the conductivity of the electrocatalyst, and the quantity and quality of active sites. Two-dimensional (2D) engineering can effectively reduce the resistance of the materials and greatly increase the number of electrochemically active sites, while heterometal doping, or the bimetal strategy, can improve the quality of active sites via changing the electronic structure of the material. Thus, the combination of the two can enhance the activity of electrocatalytic OER in all three aspects: conductivity, number and quality of active sites. However, there is currently no review on this topic. Therefore, in this review, we summarize the application of bimetallic 2D materials in electrocatalytic OER from four aspects: the structure, synthesis strategy, catalytic efficiency, and reaction mechanism.
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