Multi-electron reaction materials for sodium-based batteries

Sodium-based rechargeable batteries are very promising energy storage and conversion systems owing to their wide availability and the low cost of Na resources, which is beneficial to large-scale electric energy storage applications in future. In the context of attempting to achieve high-energy densities and low cost, multi-electron reaction materials for both cathodes and anodes are attracting significant attention due to high specific capacities involved. Here, we present a brief review on recently reported multi-electron reaction materials for sodium-based batteries. We mostly concentrate on true multi-electron reactions that involve individually valence changes greater than one per redox center, but in addition include materials in the discussion, which undergo multi-electron processes per formula unit. The theoretical gravimetric and volumetric (expanded state) capacities are studied for a broad range of examples. Then, the practically achievable volumetric energy density and specific energy of Na cells with hard carbon, sodium (Na), and phosphorus (P) anodes are compared. For this purpose, various data are recalculated and referred to the same basis cell. The results show the potential superiority of the cells using multi-electron reaction materials and provide an intuitive understanding of the practically achievable energy densities in future Na-based rechargeable batteries. However, these multi-electron reaction materials are facing several key challenges, which are preventing their high-performance in current cells. In order to overcome them, general strategies from particle design to electrolyte modification are reviewed and several examples in both cathode and anode materials using such strategies are studied. Finally, future trends and perspectives for achieving promising Na-based batteries with better performance are discussed.     

Energy transduction ferroic materials

Ferroic materials and multiferroics, characterized by their ferroic orders, provide an efficient route for the coupling control of magnetic, mechanical, and electrical subsystems in energy transduction, which aims at converting one form of energy into another. A surge of interest in the ferroic coupling effect has stemmed from its potential use as a new versatile route for energy transduction. Here, the recent progress on the use of (multi)ferroic materials is reviewed, with special emphasis on the fundamental mechanisms that dictate the energy transduction process, including piezoelectricity, pyroelectricity, electrocaloric, magnetostriction, magnetocaloric, elastocaloric, magnetoelectricity, and emerging spin-charge conversion. Research on energy transduction ferroic materials paves the way for ubiquitous energy harvesting through magneto-mechano-electric-thermal coupling mechanisms. Finally, a summary and the future prospective directions of this field are discussed.     

Fluid eddy induced piezo-promoted photodegradation of organic dye pollutants in wastewater on ZnO nanorod arrays/3D Ni foam

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Ultrathin two-dimensional materials for photo- and electrocatalytic hydrogen evolution

Sustainable hydrogen production via photocatalytic, electrocatalytic, and synergetic photoelectrocatalytic processes has been regarded as an effective strategy to address both energy and environmental crises. Due to their unique structures and properties, emerging ultrathin two-dimensional (2D) materials can bring about promising opportunities to realize high-efficiency hydrogen evolution. This review presents a critical appraisal of advantages and advancements for ultrathin 2D materials in catalytic hydrogen evolution, with an emphasis on structure–activity relationship. Furthermore, strategies for tailoring the microstructure, electronic structure, and local atomic arrangement, so as to further boost the hydrogen evolution activity, are discussed. Finally, we also present the existing challenges and future research directions regarding this promising field.     

Recent advances in emerging 2D nanomaterials for biosensing and bioimaging applications

The great success of graphene throws new light on discovering more two-dimensional (2D) layered nanomaterials that stem from atomically thin 2D sheets. Compared with a single element of graphene, emerging graphene-like 2D materials composed of multiple elements that possess more versatility, greater flexibility and better functionality with a wide range of potential applications. In this review, we provide insights into the rapidly emerging 2D materials and their biosensing and bioimaging applications in recent three years, including 2D transition metal nanomaterials, graphitic nitride materials, black phosphorus, and emerging 2D organic polymers. We first briefly highlight their unique 2D morphology and physicochemical properties and then focus on their recent applications in electrochemical biosensing, optical biosensing and bioimaging. The challenges and some thoughts on future perspectives in this field are also addressed.     

Keystroke dynamics enabled authentication and identification using triboelectric nanogenerator array

Cyber security has become a serious concern as the internet penetrates every corner of our life over the last two decades. The rapidly developing human–machine interfacing calls for an effective and continuous authentication solution. Herein, we developed a two-factor, pressure-enhanced keystroke-dynamics-based security system that is capable of authenticating and even identifying users through their unique typing behavior. The system consists of a rationally designed triboelectric keystroke device that converts typing motions into analog electrical signals, and a support vector machine (SVM) algorithm-based software platform for user classification. This unconventional keystroke device is self-powered, stretchable and water/dust proof, which makes it highly mobile and applicable to versatile working environments. The promising application of this novel system in the financial and computing industry can push cyber security to the next level, where leaked passwords would possibly be of no concern.     

Piezoelectric properties in two-dimensional materials: Simulations and experiments

The piezoelectric effect, discovered in 1880 by Jacques and Pierre Curie, effectively allows to transduce signals from the mechanical domain to the electrical domain and vice versa. For this reason, piezoelectric devices are already ubiquitous, including, for instance, quartz oscillators, mechanical actuators with sub-atomic resolution and microbalances. However, the ability to synthesize two-dimensional (2D) materials may enable the fabrication of innovative devices with unprecedented performance. For instance, many materials which are not piezoelectric in their bulk form become piezoelectric when reduced to a single atomic layer; moreover, since all the atoms belong to the surface, piezoelectricity can be effectively engineered by proper surface modifications. As additional advantages, 2D materials are strong, flexible, easy to be co-integrated with conventional integrated circuits or micro-electromechanical systems and, in comparison with bulk or quasi-1D materials, easier to be simulated at the atomistic level. Here, we review the state of the art on 2D piezoelectricity, with reference to both computational predictions and experimental characterization. Because of their unique advantages, we believe 2D piezoelectric materials will substantially expand the applications of piezoelectricity.     

Microfluidic generation of transient cell volume exchange for convectively driven intracellular delivery of large macromolecules

Efficient intracellular delivery of target macromolecules remains a major obstacle in cell engineering and other biomedical applications. We discovered a unique cell biophysical phenomenon of transient cell volume exchange using microfluidics to rapidly and repeatedly compress cells. This behavior consists of brief, mechanically induced cell volume loss followed by rapid volume recovery. We harness this behavior for high-throughput, convective intracellular delivery of large polysaccharides (2000?kDa), particles (100?nm), and plasmids while maintaining high cell viability. Successful proof of concept experiments in transfection and intracellular labeling demonstrated potential to overcome the most prohibitive challenges in intracellular delivery for cell engineering.     

Effect of 2–6 at.% Mo addition on microstructural evolution of Ti-44Al alloy

In order to understand the effect of Mo alloying on the microstructural evolution of TiAl alloy, the as-cast microstructure, heat treated microstructure characteristic, and hot compression microstructure evolution of Ti-44 A1 alloy have been studied in this work. The as-cast microstructure morphology changes from(γ+α_2)lamellar colony and β/β_0+γ mixture structure to β/β_0 phase matrix widmannstatten structure,when Mo content increases from 2 at.% to 6 at.%. Affected by the relationship between β phase and αphase, the angles between the lamellar orientation and the block β/β_0 phase are roughly at 0°, 45° and90°. Comparing with heat treatment microstructure, the hot compression microstructure contains lessβ/β_0 phase, however, the β/β_0 phase containing 2 Mo alloy and 3 Mo alloy hot compressed at 1275 ℃ has the inverse tendency. In addition,(α_2 +γ) colony is decomposed by the discontinuous transformation.     

Water wave energy harvesting and self-powered liquid-surface fluctuation sensing based on bionic-jellyfish triboelectric nanogenerator

Due to the natural working mechanism of triboelectric nanogenerators (TENGs), potential energy stored by elastic materials may not be effectively converted into electric power, post mechanical triggering. Here, we report a practical bionic-jellyfish triboelectric nanogenerator (bjTENG) with polymeric thin film as the triboelectric material, which is shape-adaptive, with a hermetic package and a unique elastic resilience structure, similar to the behavior of a jellyfish. The charge separation in the elastic resilience of this bionic-structure is based on the liquid pressure-induced contact-separation of the triboelectric layers. On the basis of the conjunction of the triboelectrification and the electrostatic induction, a sustainable and enhanced output performance of 143?V, 11.8?mA/m² and 22.1?μC/m² under a low frequency of 0.75?Hz and at a water depth of 60?cm is produced, which can be used to supply power for dozens of green LEDs or a temperature sensor directly. More significantly, bjTENG is believed to be a priority technology which is attributable to its highly sensitivity, portability, and suitability for continuous detection of water level and fluctuation. Furthermore, a wireless self-powered fluctuation sensor early-warning system, which provides exact and wireless monitoring of fluctuation of a liquid surface, is also successfully developed.     

Rapid continuous 3D printing of customizable peripheral nerve guidance conduits

Engineered nerve guidance conduits (NGCs) have been demonstrated for repairing peripheral nerve injuries. However, there remains a need for an advanced biofabrication system to build NGCs with complex architectures, tunable material properties, and customizable geometrical control. Here, a rapid continuous 3D-printing platform was developed to print customizable NGCs with unprecedented resolution, speed, flexibility, and scalability. A variety of NGC designs varying in complexity and size were created including a life-size biomimetic branched human facial NGC. In vivo implantation of NGCs with microchannels into complete sciatic nerve transections of mouse models demonstrated the effective directional guidance of regenerating sciatic nerves via branching into the microchannels and extending toward the distal end of the injury site. Histological staining and immunostaining further confirmed the progressive directional nerve regeneration and branching behavior across the entire NGC length. Observational and functional tests, including the von Frey threshold test and thermal test, showed promising recovery of motor function and sensation in the ipsilateral limbs grafted with the 3D-printed NGCs.     

Diffusion characteristics of boron and phosphorus in polycrystalline silicon

Grain boundary diffusion of dopants (boron and phosphorous) in silicon is discussed. The appropriate models and equations are presented both for semi-infinite and for thin film boundary conditions. Data reported in the literature for both thick and thin samples have generally been analyzed using models appropriate to diffusion in a homogeneous semi-infinite substrate. These data were reanalyzed using the appropriate boundary conditions and a more realistic model of the inhomogeneous nature of diffusion in polycrystalline samples. It was shown that, even though the relation between diffusion depth and time may be the same from bulk and grain boundary models, the diffusion coefficients determined from assuming the homogeneous semi-infinite solid may be several orders of magnitude in error for the pre-exponential factor, and the activation energy will also be wrong. Grain boundary diffusion coefficients for arsenic, boron and phosphorus in silicon were determined.     

Computational design and property predictions for two-dimensional nanostructures

Recent success in isolating and growing various two-dimensional (2D) materials with intriguing properties has pushed forward the search for new 2D nanostructures with novel properties. Current experimental trial-and-error methods face the fundamental challenges of low efficiency and a lack of clear guidelines. In contrast, based on state-of-the-art first-principles calculations and well-developed structural prediction algorithms, computational simulations can not only predict an increasing number of new 2D materials with desirable properties but also suggest their possible synthesis routes. Among them, many predictions, such as the growth of monolayer boron sheets (borophene), piezoelectricity in molybdenum disulfide (MoS₂), ferroelectricity in tin telluride (SnTe), topological defects in transition metal dichalcogenides, Dirac cones in borophene, and high carrier mobility and mobility anisotropy in black phosphorene, have been verified by experiments, showing the accuracy of computational approaches, as well as their power in facilitating experimental exploration in 2D flatland. To date, the rapid expansion in theoretical work has generated a large number of very important results, but the overall picture of recent progress, current challenges, and future opportunities is rarely discussed. Accordingly, this review aims at providing information about current trends and future perspectives for 2D materials research. To achieve this, the review is organized as follows: (1) discussion of structural predictions in 2D materials using borophene as an example; (2) predictions of the electronic, optical, mechanical, and magnetic properties in various 2D materials; (3) discussion of the influence of defects on the structures and properties of 2D materials; and (4) evaluation of current progress in computational simulations and perspectives for future development.     

Metallic nanoparticles for cancer immunotherapy

Cancer immunotherapy, or the utilization of the body’s immune system to attack tumor cells, has gained prominence over the past few decades as a viable cancer treatment strategy. Recently approved immunotherapeutics have conferred remission upon patients with previously bleak outcomes and have expanded the number of tools available to treat cancer. Nanoparticles – including polymeric, liposomal, and metallic formulations – naturally traffic to the spleen and lymph organs and the relevant immune cells therein, making them good candidates for delivery of immunotherapeutic agents. Metallic nanoparticle formulations, in particular, are advantageous because of their potential for dense surface functionalization and their capability for optical or heat-based therapeutic methods. Many research groups have investigated the potential of nanoparticle-mediated delivery platforms to improve the efficacy of immunotherapies. Despite the significant preclinical successes demonstrated by many of these platforms over the last twenty years, only a few metallic nanoparticles have successfully entered clinical trials with none achieving FDA approval for cancer therapy. In this review, we will discuss preclinical research and clinical trials involving metallic nanoparticles (MNPs) for cancer immunotherapy applications and discuss the potential for clinical translation of MNPs.     

Light-induced ultrafast proton-coupled electron transfer responsible for H2 evolution on silver plasmonics

Light-driven proton-coupled electron transfer (PCET) reactions on nanoplasmonics would bring temporal control of their reactive pathways, in particular, prolong their charge separation state. Using a silver nano-hybrid plasmonic structure, we observed that optical excitation of Ag-localized surface plasmon instigated electron injection into TiO₂ conduction band and oxidation of isopropanol alcoholic functionality. Femtosecond transient infrared absorption studies show that electron transfer from Ag to TiO₂ occurs in ca. 650?fs, while IPA molecules near the Ag surface undergo an ultrafast bidirectional PCET step within 400?fs. Our work demonstrates that ultrafast PCET reaction plays a determinant role in prolonging charge separation state, providing an innovative strategy for visible-light photocatalysis with plasmonic nanostructures.     

Eggshell nano-particle potential for methyl violet and mercury ion removal: Surface study and field application

A nano-scale sorbent was produced from eggshell wastes for sorption of Hg(II) and methyl violet (MV) from aqueous solutions and real wastewaters. The properties of the nano-particles were fully determined using SEM, DLS, FTIR, XRD, BET, TGA, AFM, EDAX, mapping, and TEM analyses. The adsorbent structure mainly contained carbonate and silica. The effects of influential parameters including temperature, contact time, initial contaminants concentration, sorbent dose, and initial pH on the removal efficiency were investigated. The maximum sorption efficiency of Hg(II) and MV occurred at pH of 6 and 9 and temperatures of 25 °C and 55 °C, respectively. Freundlich model could be interpreted the equilibrium data of the sorption process of both contaminants. The maximum sorption capacity of Hg(II) and MV using eggshell nano-particles was obtained as 116.27 mg/g and 123.45 mg/g, respectively. The dynamic behavior of the process was studied using two kinetic models. The sorption system performance was also examined and t_1/2 were determined as 4.34 min for Hg(II) and 4.97 min for MV. The sorption process of Hg(II) and MV was exothermic and endothermic, respectively. Effective sorption after seven cycles and successful treatment of landfill leachate and textile wastewater with eggshell nano-particles confirms its adequacy.     

Direct Z-scheme photocatalysts: Principles,synthesis, and applications

The properly designed semiconductor photocatalysts are promising materials for solving the current serious energy and environmental issues because of their ability of using sunlight to stimulate various photocatalytic reactions. Especially, the constructed direct Z-scheme photocatalysts, mimicking the natural photosynthesis system, possess many merits, including increased light harvesting, spatially separated reductive and oxidative active sites, and well-preserved strong redox ability, which benefit the photocatalytic performance. This review concisely compiles the recent progress in the fabrication, modification, and major applications of the direct Z-scheme photocatalysts; the latter include water splitting, carbon dioxide reduction, degradation of pollutants, and biohazard disinfection. It finishes with a brief presentation of future challenges and prospects in the development of direct Z-scheme photocatalytic systems.     

Controllable preparation of antimony powders by electrodeposition in choline chloride-ethylene glycol

Antimony powders with different morphologies have been prepared by electrodeposition at 313–353 K and 10–50 mA·cm^?2 in 0.1 mol·L^?1 SbCl₃ + ChCl-EG solution. The electrochemical behavior of Sb(III) on titanium electrode are studied by cyclic voltammetry. Results show that the electrochemical reduction of Sb(III) in SbCl₃ + ChCl-EG solution is a quasi-reversible process via a one-step reaction and the apparent activation energy is 50.723 kJ·mol^?1. The effects of current density and temperature on current efficiency and specific energy consumption are also investigated. The current efficiency increases with the increasing of current density and temperature. The specific energy consumption increased with the increase of current density, while decreased with the raising of temperature. When the current density is 40 mA·cm^?2 at 353 K, the current efficiency and specific energy consumption are up to 97.89% and 1251.277 kW·h·t^?1, respectively. The morphology and phase of the products are analyzed by FESEM and XRD. It demonstrates that the deposition products are pure antimony powders and their preferred crystal plane is (0 1 2). The pineal, wheat grain, badminton, dendritic, and cluster-like antimony powders can be prepared by controlling electrodeposition parameters. The particles size range of antimony powders are 0.21–261.05 μm.     

Synthesis of Pt nanocrystals with different shapes using the same protocol to optimize their catalytic activity toward oxygen reduction

Engineering the shape and thus surface structure of Pt nanocrystals is an effective strategy for optimizing their catalytic activities toward various reactions. However, different protocols are typically used to produce Pt nanocrystals with distinctive shapes, making it difficult to directly compare their catalytic activities owing to the complication of surface contamination. Here we demonstrate that Pt nanocrystals with a variety of shapes, including those enclosed with low- or high-index facets, can be synthesized using the same protocol by simply adjusting the concentration of reducing agent and/or the reaction time. Specifically, when the reducing agent was used at a relatively low concentration, Pt truncated cubes, cuboctahedrons, truncated octahedrons, and octahedrons were produced sequentially upon the increase in reaction time. When 67% more reducing agent was used, Pt cubes and concave cubes were obtained consecutively as the reaction time was prolonged. Our quantitative analysis suggests that the diversity of shape and difference in size can be resulted from the difference in reduction kinetics. In evaluating their structure–activity relationship for oxygen reduction, it was established that the high-index facets on Pt concave cubes possessed a specific activity of 6.3 and 1.3 times greater than those of Pt cubes and octahedrons exposed by {1?0?0} and {1?1?1} facets, respectively. This work not only offers a general method for the synthesis of Pt nanocrystals having diverse shapes and thus different types of facets but also highlights the significance of reduction kinetics in controlling the structure evolution of other metal nanocrystals.