Negatively Charged Holey Titania Nanosheets Added Electrolyte to Realize Dendrite-Free Lithium Metal Battery.

Electrolyte modulation and electrode structure design are two common strategies to suppress dendrites growth on Li metal anode. In this work, a self-adaptive electrode construction method to suppress Li dendrites growth is reported, which merges the merits of electrolyte modulation and electrode structure design strategies. In detail, negatively charged titania nanosheets with densely packed nanopores on them are prepared. These holey nanosheets in the electrolyte move spontaneously onto the anode under electrical field, building a mesoporous structure on the electrode surface. The as-formed porous electrode has large surface area with good lithiophilicity, which can efficiently transfer lithium ion (Li+ ) inside the electrode, and induce the genuine lithium plating/stripping. Moreover, the negative charges and nanopores on the sheets can also regulate the lithium-ion flux to promote uniform deposition of Li metal. As a result, the symmetric and full cells using the holey titania nanosheets containing electrolyte, show much better performance than the ones using electrolyte without holey nanosheets inside. This work points out a new route for the practical applications of Li-metal batteries.

3D Lithiophilic CuZrAg Metallic Glass Based-Current Collector for High-Performance Lithium Metal Anode.

Lithium metal anodes face several challenges in practical applications, such as dendrite growth, poor cycle efficiency, and volume variation. 3D hosts with lithiophilic surfaces have emerged as a promising design strategy for anodes. In this study, inspiration from the intrinsic isotropy, chemical heterogeneity, and wide tunability of metallic glass (MG) is drew to develop a 3D mesoporous host with a lithiophilic surface. The CuZrAg MG is prepared using the scalable melt-spinning technique and subsequently treated with a simple one-step chemical dealloying method. This resultes in the creation of a host with a homogeneously distributed abundance of lithium affinity sites on the surface. The excellent lithiophilic property and capability for uniform lithium deposition of the 3D CuZrAg electrode have been confirmed through theoretical calculations. Therefore, the 3D CuZrAg electrode displays excellent cyclic stability for over 400 cycles with 96% coulomb efficiency, and ultra-low overpotentials of 5 mV for over 2000 h at 1.0 mA cm-2 and 1.0 mAh cm-2 . Additionally, the full cells partied with either LiFePO4 or LiNi0.8 Co0.1 Mn0.1 O2 cathode deliver exceptional long-term cyclability and rate capability. This work demonstrates the great potential of metallic glass in lithium metal anode application.

Ternary Lithium Nickel Boride with 1D Rapid-Ion-Diffusion Channels as an Anode for Use in Lithium-Ion Batteries.

Anode materials with high-rate performances and good electrochemical stabilities are urgently required for the grid-scale application of lithium-ion batteries (LIBs). Theoretically, transition metal borides are desirable candidates because of their appropriate working potentials and good conductivities. However, the reported metal borides exhibit poor performances owing to their lack of favorable Li+ storage sites and poor structural stabilities during long-term charging/discharging. In this work, a ternary alkali metal boride, Li1.2 Ni2.5 B2 , which displays a high Li+ storage capacity and remarkable electrochemical stability and an excellent rate performance is studied. In contrast to conventional transition metal borides, the introduction of Li atoms facilitates the formation of 1D Ni/B-based honeycomb channels during synthesis. This Ni/B framework successfully sustains the strain during Li+ intercalation and deintercalation, and thus, the optimized Li1.2 Ni2.5 B2 anode exhibits an excellent cycle stability over 500 charge/discharge cycles. This electrode also exhibits superior reversible capacities of 350, 183, and 80 mA h g-1 at 0.1, 1, and 5 A g-1 , respectively, indicating the considerable potential of the 1D Ni/B framework as a commercially available fast-charging LIB anode.

In-Situ Construction of V2 O5 Nanosheet/Nitrogen-Doped Carbon Nanosheet Heterostructures with Interfacial C─O Bridging Bonds as the Cathode Material for Zn Ion Batteries.

Layered oxides are widely used as the electrode materials for metal ion batteries. However, for large radius size ions, such as Zn2+ and Al3+ , the tightly stacked layers and poor electrical conductivity of layered oxides result in restricted number of active sites and sluggish reaction kinetics. In this work, a facile in-situ construction strategy is provided to synthesize layered oxide nanosheets/nitrogen-doped carbon nanosheet (NC) heterostructure, which shows larger interlayer spacing and better electrical conductivity than the layered oxides. As a result, the Zn2+ ion diffusion inside the interlayer gallery is greatly enhanced and the storage sites inside the gallery can be better used. Meanwhile, the NC layers and oxide nanosheets are bridged by the C─O bonds to form a stable structure, which contributes to a better cycling stability than the pure layered oxides. The optimal V2 O5 @NC-400 cathode shows a capacity of 467 mA h g-1 at 0.1 A g-1 for 300 cycles, and long-term cyclic stability of 4000 cycles at 5 A g-1 with a capacity retention of 92%. All these performance parameters are among the best for vanadium oxide-based cathode materials.

Thin-Film Composite Membranes with a Hybrid Dimensional Titania Interlayer for Ultrapermeable Nanofiltration.

The interfacial properties within a composite structure of membranes play a vital role in the separation properties and application performances. Building an interlayer can facilitate the formation of a highly selective layer as well as improve the interfacial properties of the composite membrane. However, it is difficult for a nanomaterial-based interlayer to increase the flux and retention of nanofiltration membranes simultaneously. Here, we report a nanofiltration membrane with a hybrid dimensional titania interlayer that exhibits excellent separation performance. The interlayer, composed of Fe-doped titania nanosheets and titania nanoparticles, helps the formation of an ultrathin (∼30 nm thick) and defect-free polyamide selective layer with an ideal nanostructure. The hybrid dimensional interlayer endows the membrane with a superior permeability and alleviates flux decline. In addition, the rigid interlayer framework on a PVDF support drastically improves the pressure resistance of nanofiltration membranes and shows negligible flux loss up to 1.5 MPa of pressure.

Ternary Mo2 NiB2 as a Superior Bifunctional Electrocatalyst for Overall Water Splitting.

Transition metal borides are considered as promising electrocatalysts for water splitting due to their metallic conductivity and good durability. However, the currently reported monometallic and noncrystalline multimetallic borides only show generic and monofunctional catalytic activity. In this work, the authors design and successfully synthesize highly crystalline ternary borides, Mo2 NiB2 , via a facile solid-state reaction from pure elemental powders. The as-synthesized Mo2 NiB2 exhibits very low overpotentials for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), that is, 280 and 160 mV to reach a current density of 10 mA cm-2 , in alkaline media. These values are much lower from the ones observed over monometallic borides, that is, Ni2 B and MoB, and the lowest among all nonprecious metal borides. By loading Mo2 NiB2 onto Ni foams as both cathode and anode electrode for overall water splitting applications, a low cell voltage of 1.57 V is required to achieve a current density of 10 mA cm-2 , comparable with the value required from the Pt/C||IrO2 /C couple (1.56 V). The proposed synthesis strategy can be used for the preparation of cost-effective, multi-metallic crystalline borides, as multifunctional electrocatalysts.

Understanding the Surface Reconstruction on Ternary Wx CoBx for Water Oxidation and Zinc-Air Battery Applications.

Here, the synthesis of a series of pure phase metal borides is reported, including WB, CoB, WCoB, and W2 CoB2 , and their surface reconstruction is studied under the electrochemical activation in alkaline solution. A cyclic voltammetric activation is found to enhance the activity of the CoB and W2 CoB2 precatalysts due to the transformation of their surfaces into the amorphous CoOOH layer with a thickness of 3-4 nm. However, such surface transformation does not happen on the WB and WCoB due to their superior structure stability under the applied voltage, highlighting the importance of metal components for the surface reconstruction process. It is found that, compared with CoB, the W2 CoB2 surface shows a quicker reconstruction with a larger active surface area due to the selective leaching of the W from its surface. In the meantime, the metallic W2 CoB2 core underneath the CoOOH layer shows a better promotion of its oxygen evolution reaction (OER) performance than CoB. Therefore, the ternary W2 CoB2 shows better OER performance than the CoB, as well as the WB and WCoB. It is also found that the mixture of W2 CoB2 with Pt/C as the catalysts in air electrode for rechargeable Zn-air battery (ZAB), shows better performance than the IrO2 -Pt/C couple-based ZAB.

Bridging 1D Inorganic and Organic Synthesis to Fabricate Ultrathin Bismuth-Based Nanotubes with Controllable Size as Anode Materials for Secondary Li Batteries.

The growth of ultrathin 1D inorganic nanomaterials with controlled diameters remains challenging by current synthetic approaches. A polymer chain templated method is developed to synthesize ultrathin Bi2 O2 CO3 nanotubes. This formation of nanotubes is a consequence of registry between the electrostatic absorption of functional groups on polymer template and the growth habit of Bi2 O2 CO3 . The bulk bismuth precursor is broken into nanoparticles and anchored onto the polymer chain periodically. These nanoparticles react with the functional groups and gradually evolve into Bi2 O2 CO3 nanotubes along the chain. 5.0 and 3.0 nm tubes with narrow diameter deviation are synthesized by using branched polyethyleneimine and polyvinylpyrrolidone as the templates, respectively. Such Bi2 O2 CO3 nanotubes show a decent lithium-ion storage capacity of around 600 mA h g-1 at 0.1 A g-1 after 500 cycles, higher than other reported bismuth oxide anode materials. More interestingly, the Bi materials developed herein still show decent capacity at very low temperatures, that is, around 330 mA h g-1 (-22 °C) and 170 mA h g-1 (-35 °C) after 75 cycles at 0.1 A g-1 , demonstrating their promising potential for practical application in extreme conditions.

Preparation of 2D material dispersions and their applications.

Extensive research on two-dimensional (2D) materials has triggered the renaissance of an old topic, that is, the intercalation and exfoliation of layer materials. Such top-down exfoliation produced 2D materials and their dispersions have several advantages including low cost, scalable production capability, solution processability, and versatile functionalities stemming from the large number of species of layer materials, and show promising potential in many applications. In recent years, many new methods have been developed for exfoliating layer materials to 2D materials for different application purposes. In this review the different exfoliation approaches are first systematically analyzed from the viewpoint of methodology, and the advantages and disadvantages of each method are compared. Second, the assembly of exfoliated 2D materials into macrostructures by solution-based techniques is summarized. Third, the state-of-the-art applications of 2D material dispersions and their assemblies in electronics and optoelectronics, electrocatalysis, energy storage, etc., are discussed. Finally, insights and perspectives on current research challenges and future opportunities regarding the exfoliation and applications of 2D materials in dispersions are considered.

Tuning the surface charge of 2D oxide nanosheets and the bulk-scale production of superlatticelike composites.

The surface charge of various anionic unilamellar nanosheets, such as graphene oxide (GO), Ti0.87O2(0.52-), and Ca2Nb3O10(-) nanosheets, has been successfully modified to be positive by interaction with polycations while maintaining a monodispersed state. A dilute anionic nanosheet suspension was slowly added dropwise into an aqueous solution of high molecular weight polycations, which attach on the surface of the anionic nanosheets via electrostatic interaction. Surface modification and transformation to positively charged nanosheets were confirmed by various characterizations including atomic force microscopy and zeta potential measurements. Because the sizes of the polycations used are much larger than the nanosheets, the polymer chains may run off the nanosheet edges and fold to the fronts of the nanosheets, which could be a reason for the continued dispersion of the modified nanosheets in the suspension. By slowly adding a suspension of polycation-modified nanosheets and pristine anionic nanosheet dropwise into water under suitable conditions, a superlatticelike heteroassembly can be readily produced. Characterizations including transmission electron microscopy and X-ray diffraction measurements provide evidence for the formation of the alternately stacked structures. This approach enables the combination of various pairs of anionic nanosheets with different functionalities, providing a new opportunity for the creation of unique bulk-scale functional materials and their applications.

A Metal Coordination Number Determined Catalytic Performance in Manganese Borides for Ambient Electrolysis of Nitrogen to Ammonia.

A new strategy that can effectively increase the nitrogen reduction reaction performance of catalysts is proposed and verified by tuning the coordination number of metal atoms. It is found that the intrinsic activity of Mn atoms in the manganese borides (MnBx) increases in tandem with their coordination number with B atoms. Electron-deficient boron atoms are capable of accepting electrons from Mn atoms, which enhances the adsorption of N2 on the Mn catalytic sites (*) and the hydrogenation of N2 to form *NNH intermediates. Furthermore, the increase in coordination number reduces the charge density of Mn atoms at the Fermi level, which facilitates the desorption of ammonia from the catalyst surface. Notably, the MnB4 compound with a Mn coordination number of up to 12 exhibits a high ammonia yield rate (74.9 ± 2.1 µg h-1 mgcat -1) and Faradaic efficiency (38.5 ± 2.7%) at -0.3 V versus reversible hydrogen electrode (RHE) in a 0.1 m Li2SO4 electrolyte, exceeding those reported for other boron-related catalysts.

Nano-Graphite Prepared by Rapid Pulverization as Anode for Lithium-Ion Batteries.

Reducing the particle size of active material is an effective solution to the poor rate performance of the lithium-ion battery. In this study, we proposed a facile strategy for the preparation of nano-graphite as an anode for a lithium-ion battery via the rapid mechanical pulverization method. It is the first time that diamond particle was selected as the medium to achieve high preparation efficiency and low energy consumption. The as-prepared nano-graphite with the size from 10 to 300 nm displays an intact structure and high specific surface area. The introduced oxygen atoms increased the wettability of nano-graphite electrode and lowered its polarization. The nano-graphite prepared from three hours of grinding shows an excellent reversible capacity of 191 mAh g-1, at a rate of 5 C, after 480 cycles, along with an increase of 86% in capacity, at 1 C, in comparison with pristine graphite. The highlight of this strategy is to optimize the current preparation method. The good electrochemical performance comes from the combined effect of nano-scale particle size, large specific surface area, and continuous mesopores.

Photo-promoted in situ reduction and stabilization of Pd nanoparticles by H2 at photo-insensitive Sm2O3 nanorods.

Controlled synthesis of noble metal nanoparticles with well-defined size and good dispersion on supports has been a long-standing challenge in heterogeneous catalysis. Here we report a facile photo-assisted H2in situ reduction process to synthesize monodispersed Pd nanoparticles with 2-4 nm size on photo-insensitive Sm2O3 rare-earth metal oxide with nanorod morphology. Thanks to the contribution of UV irradiation, the photoelectrons generation in the Sm2O3 support accelerates the H2 reduction of Pd2+ ions into Pd0 and stabilize the growth of very small Pd nanoparticles homogeneously dispersed on the support. The homogeneous distribution of the Pd NPs on the surface of Sm2O3 is most likely attributed to the profuse nucleation sites created by the UV irradiation and the abundance of hydroxyl groups on the support. The hydrogenation of styrene to ethylbenzene was studied as a model reaction. As a result, the UV radiated sample shows an excellent TOF value of 7419 h-1, which is quadruple of the sample without UV irradiation, under the condition of 0.1 MPa H2 at a content of 1.0 wt% Pd. Besides, UV radiated sample shows a negligible performance degradation during the repeated cycling process. This photo-promoted H2 reduction process provides a convenient and straightforward route for assembling materials with novel structures and functions for nanotechnology applications.

Is the Plastic Pandemic a Greater Threat to Humankind than COVID-19?

The advent of the COVID-19 pandemic has initiated a radical attention shift of society toward the severe consequences it has had over human health, shadowing a symmetrically, if not more, important issue of the rapid intensification in the amount of plastic waste that has been generated over the due course of time. Such a growth in the plastic footprint across the globe has led to a carbon positive environment with an increased amount of greenhouse gases (GHGs) released due to the processing of the waste plastic. We aim to address and provide our perception to this pressing challenge that can be decoded via the advancement of upcycling technologies, utilized and augmented worldwide. With the establishment of such sustainable policies and strategies, the global plastic footprint can be systematically mitigated, accelerating the world into economic circularity and environmental sustainability.

Electrosynthesis of Vertically Aligned Zinc Oxide Nanoflakes on 3D Porous Cu Foam Enables Dendrite-Free Li-Metal Anode.

Three dimensional (3D) hosts have been recognized as effective current collectors for Li metal anodes because of their physical suppression of the lithium dendrites growth. A lithiophilic surface layer on them could increase the Li metal nucleation sites, further regulating the genuine plating of Li metal. The current strategies to construct this lithiophilic layer on 3D structure is complex and not suitable for the scalable fabrication of Li metal anode. In this work, we developed a facile method to grow vertically aligned ZnO nanoflakes on the surface of 3D Cu foam through an electrochemical synthetic process, which physically suppressed the Li dendrites growth due to the unique structure during the Li plating/stripping process. Moreover, these lithiophilic flakes effectively increase the specific surface area of the anode and Li metal nucleation sites number, which reduces the local current densities, leading to the formation of a robust SEI and further suppressing the Li dendrites growth. Consequently, the performances of the symmetric Li plated Cu foam/Li cell and the Li plated Cu foam/LiFePO4 full cell have been greatly enhanced after the growth of vertically aligned ZnO nanoflakes on the Cu foam surface, including capacity, cycling stability, overpotential, and rate capability.

Cobalt-based MOF nanoribbons with abundant O/N species for cycloaddition of carbon dioxide to epoxides.

Chemical fixation of CO2 with epoxides is an effective option to achieve sustainable synthesis of cyclic organic carbonates. Although metal-organic frameworks (MOFs) are promising catalysts for this reaction, their low stability in aqueous solutions makes this application infeasible. In an effort to overcome this limitation, cobalt-based metal-organic framework (Co(II)MOF) nanoribbons have been prepared by coordinating the Co(II) ions with a new ligand (C16H12N4O4) full of oxygen and nitrogen moieties. Strong chemical interactions occur between the adsorbed CO2 and oxygen/nitrogen atoms in this porous MOF structure. Co(II)-MOF nanoribbons with tetra-n-butylammonium bromide acted as cocatalysts with ∼97% yield of cyclic carbonate (reaction kinetic rate of 14.7 × 106 µmol g-1 h-1) upon the cycloaddition of epichlorohydrin (ECH) to CO2 (>99% reaction selectivity under solvent-free reaction condition at 80 °C, 3 h and 1 MPa CO2 pressure). This work may open a new avenue for chemical fixation of CO2 by rational design of the components and morphology of MOF-based catalysts.

Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification Performance.

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as FeIII and CoIII, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO2 and CoO2 metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm. By monitoring of the redox reaction kinetics, the pore area density can be also tuned from ∼0.9 × 104 to ∼3.3 × 105 µm-2. The universality of this method to produce much smaller pores and higher area density than the previously reported ones has been proven in different oxide nanosheets. To demonstrate their potential applications, ultrasmall metal organic framework particles were grown inside the pores of perforated titania oxide nanosheets. The optimized hybrid film showed ∼100% rejection of methylene blue (MB) from the water. Its water permeance reached 4260 L m-2 h-1 bar-1, which is 1-3 orders of that for reported 2D membranes with good MB rejections.

Poly(ether imide) Porous Membrane Developed by a Scalable Method for High-Performance Lithium-Sulfur Batteries: Combined Theoretical and Experimental Study.

Lithium-sulfur (Li-S) batteries are one of the emerging candidates for energy storage systems due to their high theoretical energy density and the abundance/nontoxicity/low cost of sulfur. Compared with conventional lithium-ion batteries, multiple new challenges have been brought into this advanced battery system, such as polysulfide shuttling in conventional polyolefin separators and undesired lithium dendrite formation of the Li metal anode. These issues severely affect the cell performance and impede their practical applications. Herein, we develop a poly(ether imide) (PEI)-based membrane with a sponge-like pore morphology as the separator for the Li-S battery by a simplified phase inversion method. This new separator can not only alleviate the new challenges in Li-S batteries but also exhibit excellent ion conductivity, better thermal stability, and higher mechanical strength compared to those of the conventional polypropylene (PP) separator. A combined experimental and theoretical study indicates that the sponge-like morphology of the PEI membrane and its good wettability toward the electrolyte can facilitate uniform ion transportation and suppress dendrite growth. Meanwhile, the PEI molecules exhibit a strong interaction with polysulfides and avoid their shuttling effectively. As a result, the PEI-based Li-S battery shows a much better performance from various aspects (capacity, rate capability, and cycling stability) than that of the PP-based Li-S battery, especially at high charge/discharge current densities and high sulfur loadings. Since the developed PEI membrane can be easily scaled up, this work may accelerate the practical applications of Li-S batteries from the point of separators.

Constructing Cu-CuO heterostructured skin on Cu cubes to promote electrocatalytic ammonia production from nitrate wastewater.

Electroreducting nitrate (NO3-) into ammonia (NH3), i.e. NO3-RA, can not only relieve NO3- pollution but also produce high value-added NH3. Cu-based species have been taken as a promising catalyst for NO3-RA because of their relatively high Faradaic efficiency (FE), benefiting from the weak side hydrogen evolution reaction (HER). However, their NH3 yield rates are still unsatisfactory due to the multiple electron paths of NO3-RA. Herein, we report a Cu cube with Cu-CuO heterostructured skin, prepared by electrochemically induced reconstruction from a Cu2O cube. This novel Cu-based catalyst presents a mol-level NH3 yield rate of 3.17 mol h-1 g-1 ranking at the top level among non-noble metal catalysts and an ultrahigh FE of 98.7 %. These excellent performances attribute to the Cu-CuO heterostructured skin of Cu cubes, which has favorable energy for the hydrogenation of *NO to *NOH during the NO3-RA process and an unfavorable one for HER. For the NO3- removal of real river water, this novel Cu-based catalyst presents a high NO3- removal rate of 95.5 % after the NO3-RA test for 12 h, resulting in a lower NO3- concentration than the maximum residual amount of NO3- in drinking water limited by WHO and China. This study provides a feasible strategy by the electrochemical reconstruction method to prepare superior Cu-based electrocatalysts with mol-level NO3-RA performances for the purification of nitrate wastewater.

Mass production of 2D materials by intermediate-assisted grinding exfoliation.

The scalable and high-efficiency production of 2D materials is a prerequisite to their commercial use. Currently, only graphene and graphene oxide can be produced on a ton scale, and the inability to produce other 2D materials on such a large scale hinders their technological applications. Here we report a grinding exfoliation method that uses micro-particles as force intermediates to resolve applied compressive forces into a multitude of small shear forces, inducing the highly efficient exfoliation of layer materials. The method, referred to as intermediate-assisted grinding exfoliation (iMAGE), can be used for the large-scale production of many 2D materials. As an example, we have exfoliated bulk h-BN into 2D h-BN with large flake sizes, high quality and structural integrity, with a high exfoliation yield of 67%, a high production rate of 0.3 g h-1 and a low energy consumption of 3.01 × 106 J g-1. The production rate and energy consumption are one to two orders of magnitude better than previous results. Besides h-BN, this iMAGE technology has been used to exfoliate various layer materials such as graphite, black phosphorus, transition metal dichalcogenides, and metal oxides, proving its universality. Molybdenite concentrate, a natural low-cost and abundant mineral, was used as a demo for the large-scale exfoliation production of 2D MoS2 flakes. Our work indicates the huge potential of the iMAGE method to produce large amounts of various 2D materials, which paves the way for their commercial application.