Latest ArticlesAs an important anode material for fast-charging Li-ion batteries (LIBs), black phosphorus (BP) has attracted extensive attention. Black phosphorene nanotubes (BPNTs) can be theoretically produced by rolling up the black phosphorene nanosheet along armchair (a-BPNTs) and zigzag (z-BPNTs) directions. The effects of curvature, chirality, Li-storage concentrations and strain stress on the Li-storage performance such as Li diffusion barriers and mechanical stabilities of BPNTs are mainly investigated by first principles calculations. The theoretical calculations predict that the a-BPNTs and z-BPNTs have good maximum Li-storage capacities, and the z-BPNTs exhibit better flexibility than a-BPNTs. The mechanical stabilities and Li-migration are all related to the curvature of BPNTs. Additionally, both a-BPNTs and z-BPNTs exhibit fast Li-ion conductivity along the c-axis direction. Moreover, the average Poisson's ratio of a-BPNTs (0.68) is larger than that of z-BPNTs (0.17), indicating that the strain stress is more difficult to apply on a-BPNTs than z-BPNTs. Our calculations predict that the a-BPNTs can afford ultrafast kinetic rate for fast-charging and high-power LIBs, while the z-BPNTs can provide extra capacity for high-energy LIBs.
Two-dimensional (2D) materials with honeycomb, kagome or star lattice have been intensively studied because electrons in such lattices could give rise to exotic quantum effects. In order to improve structural diversity of 2D materials to achieve unique properties, here we propose a new quasi-2D honeycomb-star-honeycomb (HSH) lattice based on first-principles calculations. A carbon allotrope named HSH-C10 is designed with the HSH lattice, and its mechanical properties have been intensively investigated through total energy, phonon dispersion, ab initio molecular dynamic simulations, as well as elastic constants calculations. Besides the classical covalent bonds, there is an interesting charge-shift bond in this material from the chemical bonding analysis. Additionally, through the analysis of electronic structure, HSH-C10 is predicted to be a semiconductor with a direct band gap of 2.89 eV, which could combine the desirable characteristics of honeycomb and star lattice. Importantly, by modulating coupling strength, a flat band near the Fermi level can be obtained in compounds HSH-C6Si4 and HSH-C6Ge4, which have potential applications in superconductivity. Insight into such mixed lattice would inspire new materials with properties we have yet to imagine.
Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choices of cathode materials with satisfactory cycling performance. The polyoxometalates perform formidable redox stability and able to participate in multi-electron transfer, which was well-suited for energy storage. Herein, a bi-component polyoxometalate-derivative KNiVO (K2[Ni(H2O)6]2[V10O28]·4H2O polyoxometalates after annealing) is firstly demonstrated as a cathode material for aqueous ZIBs. The layered KV3O8 (KVO) In the bi-component material constitutes Zn2+ migration and storage channels (K+ were substantially replaced by Zn2+ in the activation phase), and the three-dimensional NiV3O8 (NiVO) part acts as skeleton to stabilize the ion channels, which assist the cell to demonstrate a high-rate capacity and specific energy of 229.4 mAh/g and satisfactory cyclability (capacity retention of 99.1% after 4500 cycles at a current density of 4 A/g). These results prove the feasibility of POM as cathode materials precursor and put forward a novel pattern of the Zn2+ storage mechanism in the activated-KNiVO clusters, which also provide a new route for selecting or designing high-performance cathode for aqueous ZIBs and other advanced battery systems.
Self-supported transition-metal single-atom catalysts (SACs) facilitate the industrialization of electrochemical CO2 reduction, but suffer from high structural heterogeneity with limited catalytic selectivity. Here we present a facile and scalable approach for the synthesis of self-supported nickel@nitrogen-doped carbon nanotubes grown on carbon nanofiber membrane (Ni@NCNTs/CFM), where the Ni single atoms and nanoparticles (NPs) are anchored on the wall and inside of nitrogen-doped carbon nanotubes, respectively. The side effect of Ni NPs was further effectively inhibited by alloying Ni with Cu atoms to alter their d-band center, which is theoretically predicted and experimentally proved. The optimal catalyst Ni9Cu1@NCNTs/CFM exhibits an ultrahigh CO Faradic efficiency over 97% at −0.7 V versus reversible hydrogen electrode. Additionally, this catalyst shows excellent mechanical strength which can be directly used as a self-supporting catalyst for Zn-CO2 battery with a peak power density of ~0.65 mW/cm2 at 2.25 mA/cm2 and a long-term stability for 150 cycles. This work opens up a general avenue to facilely prepare self-supported SACs with unitary single-atom site for CO2 utilization.
Aqueous phase synthesized ternary I–III–VI2 Quantum dots (QDs) are getting more and more attention in biology researches, for their good biocompatibility and easy-to-adjust fluorescence properties. However, the quantum yield (QY) of these aqueous phase synthesized QDs are often pretty low, which seriously hindered their further applications in this field. In general, the ripening of the QDs helps to enhance their QY, closely related to the ripening temperature. But it is still hard to precisely control the fluorescence performance of the QDs products, due to the difficulties in precise temperature control and cumbersome temperature adjusting operations in batch reactors. Here we proposed an integrated droplet microfluidic chip for the automated and successive AgInS2 QDs synthesis and ripening, with both temperatures controlled independently, precisely but easily. Taking advantage of the space-time transformation of the droplet microfluidic chips, the suitable temperature combination for AgInS2 QDs synthesis and ripening was studied, and the high-performance AgInS2 QDs were obtained. In addition, the reason for the decrease of QY of AgInS2 QDs at higher ripening temperature was also explored.
Photocatalytic optical fibers are promising for the degradation of gaseous and volatile pollutants in air due to their high specific surface area, high light utilization efficiency, easy regeneration, and sustainability. In particular, photocatalytic optical fibers have proven highly useful for the removal and conversion of different kinds of air pollutants in air. However, these fibers suffer from low photocatalytic degradation efficiencies. In this review, we have focused on introducing photocatalytic quartz optical fibers and photocatalytic plastic optical fibers for the degradation and transformation of gas-phase air pollutants. The principle of photocatalytic optical fibers and main methods for improving their photocatalytic and light utilization efficiencies based on semiconductor photocatalytic coatings are summarized. Moreover, the Langmuir-Hinshelwood kinetic rate equation was summarized to analyze the photocatalytic reduction of gaseous pollutants. Finally, an outlook on the future of photocatalytic optical fibers toward the removal and conversion of gaseous air pollutants is discussed.
Owing to frequent environmental monitoring of tetrabromobisphenol-A (TBBPA) analogs and their potential ecotoxicological effects on organisms, analysis of trace levels of TBBPA analogs with more non-polar and less water-soluble characteristics is of great significance for studying their environmental behaviors and toxic effects. Herein, a fast and sensitive technique is developed for directly detecting aqueous TBBPA analogs, including TBBPA mono(allyl ether) (TBBPA-MAE), TBBPA mono(2,3-dibromopropyl ether) (TBBPA-MDBPE), TBBPA mono(2-hydroxyethyl ether) (TBBPA-MHEE) and TBBPA mono(glycidyl ether) (TBBPA-MGE), by combining solid phase microextraction (SPME) based on porous covalent organic frameworks (Porous-COFs) with constant flow desorption ionization-mass spectrometry (CFDI-MS). As chromatographic separation is replaced by constant flow desorption, each sample can be analyzed within 7 min. The hierarchical porous structures (microporous, mesoporous and macroporous) of COFs lead to the enhanced mass transfer and the easier accessibility of active sites to TBBPA analogs, so that the extraction efficiency is 2.3–3.6 times higher than pure microporous COFs, and far superior to commercial coatings. The detection limit and quantification limit of this method are 0.1–1 and 0.4–3.2 ng/L, respectively. Ultra-trace levels of TBBPA analogs from 5.0 ng/L to 66 ng/L have been successfully detected in river and sea water samples, showing great potential for subsequent studies of their environmental behaviors and toxicological effects
In this work, a conductive thin film composite forward osmosis (TFC-FO) membrane was firstly prepared via vacuum filtering MXenes nanolayer on the outer surface of polyethersulfone membrane followed by interfacial polymerization in the other side. Moreover, its feasibility of mitigating organic fouling under electric field was evaluated. Results indicated that the addition of MXenes greatly reduced the electric resistance of membrane from 2.1 × 1012 Ω to 46.8 Ω, enhanced the membrane porosity and promoted the membrane performance in terms of the ratio of water flux to reverse salt flux. The modified TFC-FO membrane presented the optimal performance with 0.47 g/m2 loading amount of MXenes. Organic fouling experiments using sodium alginate (SA) and bovine serum albumin (BSA) as representative demonstrated that the introduction of MXenes could effectively enhance the anti-fouling ability of TFC-FO membrane under the electric field of 2 V. The interelectron repulsion hindered organic foulants attaching into membrane surface and thus effectively alleviated the membrane fouling. More importantly, the modified TFC-FO membrane showed good stability during the fouling experiment of 10 h. In all, our work proved that introducing MXenes into the porous layer of support is feasible to alleviate organic fouling of FO membrane.
Semiconductor-employed photocatalytic CO2 reduction has been regarded as a promising approach for environmental-friendly conversion of CO2 into solar fuels. Herein, TiO2/Cu2O composite nanorods have been successfully fabricated by a facile chemical reduction method and applied for photocatalytic CO2 reduction. The composition and structure characterization indicates that the Cu2O nanoparticles are coupled with TiO2 nanorods with an intimate contact. Under light illumination, all the TiO2/Cu2O composite nanorods enhance the photocatalytic CO2 reduction. In particular, the TiO2/Cu2O-15% sample exhibits the highest CH4 yield (1.35 µmol g-1 h-1) within 4 h irradiation, and it is 3.07 and 15 times higher than that of pristine TiO2 nanorods and Cu2O nanoparticles, respectively. The enhanced photoreduction capability of the TiO2/Cu2O-15% is attributed to the intimate construction of Cu2O nanoparticles on TiO2 nanorods with formed p-n junction to accelerate the separation of photogenerated electron-hole pairs. This work provides a reference for rational design of a p-n heterojunction photocatalyst for CO2 photoreduction.
Superwetting membranes have emerged as promising materials for the efficient treatment of oily wastewater. Typically, superwetting membranes can be developed by ingeniously chemical modification and topographical structuration of microporous membranes. Herein, we report the hierarchical assembly of metal-phenolic-polyplex coating to manipulate membrane surface superwettability by integrating metal-phenolic (FeⅢ-tannic acid (TA)) assembly with polyplex (tannic acid-polyethylenimine (PEI)) assembly. The proposed Fe-TA-PEI coating can be deposited on microporous membrane via simply dipping into FeⅢ-TA-PEI co-assembly solution. Based on the catechol chemistry, the coordination complexation of FeⅢ and TA develops metal-phenolic networks to provide hydrophilic chemistries, and the electrostatic complexation of TA and PEI generates nanoconjugates to impart hierarchical architectures. Benefiting from the synergy of hydrophilic chemistries and hierarchical architectures, the resulting PVDF/Fe-TA-PEI membrane exhibits excellent superhydrophilicity (~0°), underwater superoleophobicity (~150°) and superior anti-oil-adhesion capability. The superhydrophilicity of PVDF/Fe-TA-PEI membrane greatly promotes membrane permeability, featuring water fluxes up to 5860 L m−2 h−1. The underwater superoleophobicity of PVDF/Fe-TA-PEI membrane promises potential flux (3393 L m−2 h−1), high separation efficiency (99.3%) and desirable antifouling capability for oil-in-water emulsion separation. Thus, we highlight the reported hierarchical metal-phenolic-polyplex assembly as a straightforward and effective strategy that enables the synchronous modulation of surface chemistry and topography toward superwetting membranes for promising high-flux and antifouling oil-water separation.
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