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Li‒S batteries have shown great potential as secondary energy batteries. However, the side reaction between Li anodes and polysulfides seriously limited their practical application. Herein, the artificial protective film, which is consisted of Li-Nafion and TiO2, was designed and successfully prepared to achieve a corrosion-resistant Li anode in Li-S battery. In the composite protective film, the Li-Nafion could efficiently prevent the contact between Li anodes and polysulfides, and the incorporation of TiO2 nanoparticles into the Nafion could significantly increase the ionic conductivity and mechanical strength of the protective film. Li-Li symmetric cells with an optimal artificial protective film exhibited an extended cycle-life of 750 h at a current density of 1 mA/cm2 in Li2S8 electrolyte. Moreover, the Li‒S full battery with an optimal protective Li anode exhibited higher capacity retention of 777.4 mAh/g after 100 cycles at 0.1 C as well as better rate performance than the cell with a pure Li anode. This work provides alternative insights to suppress the side reaction for Li‒S batteries with high capacity retention.

Reasonable structure design of an absorber is important to its microwave absorption property. Herein we design a “non-standard” yolk-shelled nanostructure with a morphology mediated between core-shelled and yolk-shelled structures using NixSy sphere as yolk and N, S-codoped carbon as shell (n-NixSy@NSC). The n-NixSy@NSC possesses merits of both core-shelled and yolk-shelled nanostructures, resulted in its excellent microwave absorption performance. The optimal n-NixSy@NSC has a minimal reflection loss of −37.2 dB as the matching thickness is only 1.5 mm, superior to that of the bared NiS2 sphere and previously reported absorbers with similar structure and composition. The experimental results and density functional theory calculations indicate that the enhanced microwave absorption performance of the n-NixSy@NSC is attributed to the increased electrical conductivity and interfacial polarization relaxation as well as the improved impedance matching feature. Our results highlight an efficient strategy for design and fabrication of high-performance microwave absorbers.

The lithium-sulfur (Li-S) battery is regarded as a promising secondary battery. However, constant parasitic reactions between the Li anode and soluble polysulfide (PS) intermediates significantly deteriorate the working Li anode. The rational design to inhibit the parasitic reactions is plagued by the inability to understand and regulate the electrolyte structure of PSs. Herein, the electrolyte structure of PSs with anti-reductive solvent shells was unveiled by molecular dynamics simulations and nuclear magnetic resonance. The reduction resistance of the solvent shell is proven to be a key reason for the decreased reactivity of PSs towards Li. With isopropyl ether (DIPE) as a cosolvent, DIPE molecules tend to distribute in the outer solvent shell due to poor solvating power. Furthermore, DIPE is more stable than conventional ether solvents against Li metal. The reactivity of PSs is suppressed by encapsulating PSs into anti-reductive solvent shells. Consequently, the cycling performance of working Li-S batteries was significantly improved and a pouch cell of 300 Wh kg-1 was demonstrated. The fundamental understanding in this work provides an unprecedented ground to understand the electrolyte structure of PSs and the rational electrolyte design in Li-S batteries.

Considering serious exhausted non-renewable energy resources and electromagnetic radiation pollution issues, it is quite urgent to exploit multifunctional material for realizing both the conversion sustainable energy sources and protection of electromagnetic radiation pollution. Herein, we develop a facile and high-yield preparation route to fabricate a multifunctional material consisted of CoFe alloy nanoparticles encapsulated in nitrogen doped carbon nanotubes arrays grown on both sides of reduced graphene oxide (CoFe@N-CNT/rGO). CoFe@N-CNT/rGO displays excellent properties in the field of rechargeable Zn-air battery and electromagnetic wave absorption. CoFe@N-CNT/rGO shows bifunctional electrocatalytic performances toward oxygen reduction reaction and oxygen evolution reaction, favorably comparable to that of commercial catalysts (Pt/C and IrO2). Furthermore, the assembled liquid and all-solid-state rechargeable Zn-air batteries with CoFe@N-CNT/rGO as air cathode display good charging–discharging performance. As electromagnetic wave absorbing material, CoFe@N-CNT/rGO shows the minimal reflection loss of −33.2 dB at 13.3 GHz, superior to reported carbon-based electromagnetic wave absorbing materials. Based on excellent electromagnetic absorption performance, electromagnetic energy conversion device is designed to realize reasonable utilization and conversion of the absorbed electromagnetic energy. These encouraging results lay a solid foundation for development the multifunctional material and provide an effective strategy for simultaneously solving energy crisis and electromagnetic radiation problems.

Lithium-sulfur (Li-S) batteries are one of the most promising rechargeable storage devices due to the high theoretical energy density. However, the low areal sulfur loading impedes their commercial development. Herein, a 3D free-standing sulfur cathode scaffold is rationally designed and fabricated by coaxially coating polar Ti3C2Tx flakes on sulfur-impregnated carbon cloth (Ti3C2Tx@S/CC) to achieve high loading and high energy density Li-S batteries, in which, the flexible CC substrate with highly porous structure can accommodate large amounts of sulfur and ensure fast electron transfer, while the outer-coated Ti3C2Tx can serve as a polar and conductive protective layer to further promote the conductivity of the whole electrode, achieve physical blocking and chemical anchoring of lithium-polysulfides as well as catalyze their conversion. Due to these advantages, at a sulfur loading of 4 mg cm−2, Li-S cells with Ti3C2Tx@S/CC cathodes can deliver outstanding cycling stability (746.1 mAh g−1 after 200 cycles at 1 C), superb rate performance (866.8 mAh g−1 up to 2 C) and a high specific energy density (564.2 Wh kg−1 after 100 cycles at 0.5 C). More significantly, they also show the commercial potential that can compete with current lithium-ion batteries due to the high areal capacity of 6.7 mAh cm−2 at the increased loading of 8 mg cm−2.

Intrinsic polysulfide shuttling is the most fatal problem with Li-S batteries but it can be suppressed by functionalizing the separators with strong lithium polysulfide absorbents. Carbon nanotube (CNT)-supported MoSe2 nanoflakes with a large interlayer spacing were coated on a commercial polypropylene separator to build an efficient barrier (M/C-PP) to polysulfide shuttling for Li-S batteries. The battery with the separator had initial specific capacities of 1 485 and 880 mAh g−1 at 0.1 and 2 C, respectively, and an excellent long-term cycling stability with a low decay rate of 0.093% per cycle at 0.5 C after 300 cycles. This excellent performance was attributed to the strong adsorption of polysulfides by MoSe2 and the fast charge transport channels provided by the CNTs.

MXenes are well known for their potential application in supercapacitors due to their high-rate intercalation pseudocapacitance and long cyclability. However, the reported low capacity of pristine MXenes hinders their practical application in lithium-ion batteries. In this work, a robust strategy is developed to control the functional groups of Nb2CTx MXene. The capacity of pristine Nb2CTx MXene can be significantly increased by Li+ intercalation and surface modification. The specific capacity of the treated Nb2CTx is up to 448 mAh g−1 at 0.05 A g−1, and at a large current density of 2 A g−1 remains a high reversible capacity retention rate of 75% after an ultra-long cycle of 2000 cycles. These values exceed most of the reported pristine MXenes (including the most studied Ti3C2Tx) and carbon-based materials. It demonstrates that this strategy has great help to improve the electrochemical performance of pristine MXene, and the results enhance the promise of MXenes in the application of lithium-ion batteries.

Cost-effective electrocatalysts are imperative to the large-scale hydrogen evolution reaction. Herein, 1T/2H–MoSe2/Ti3C2 composites are integrated via a hydrothermal method by taking advantage of the tunable phases of MoSe2 and high conductivity of Ti3C2. Consequently, the 1T/2H–MoSe2/Ti3C2 composites exhibit an optimal overpotential of 150 mV at 10 mA cm−2, a low Tafel slope of 90 mV dec−1, and a steady catalytic activity for over 30 h in an alkaline environment. The improved HER performances can be ascribed to the introduction of the Ti3C2 support in a proper proportion, which not only makes the charge transfer process more convenient but also helps the dispersion of MoSe2. Furthermore, the formation of MoSe2/Ti3C2 heterogeneous interfaces and the synergistic effects stemming from the intimate interactions between the individual components ultimately boost the H2O dissociation in the Volmer step. This study indicates that Ti3C2 is an ideal conductive support for improving HER catalytic activity, and paves a new way for other transition metal selenides and MXenes to build highly efficient HER electrocatalysts.

Lightweight and low filler loading of electromagnetic wave absorption materials remain a huge challenge under the premise of strong absorption and broad absorption band. Here, we offer a facile strategy to prepare the ultralight self-supported N-doped reduced graphene oxide aerogels containing pod-like N-doped carbon nanotubes and FeNi@N-doped graphene layer core-shell nanoparticles for high-performance electromagnetic wave absorbing materials. The mass density of the ultralight aerogels is 0.0131 g cm−3, greatly lower than those of activated carbons. With a filling loading of only 10 wt% and the matching thickness of 2.0 mm, the minimal reflection loss of aerogels reaches −39.39 dB at 13.28 GHz. When the matching thickness is smaller than 2.0 mm (1.6–2.0 mm), the minimal reflection loss values of the optimized aerogels can still exceed −20 dB superior to most of reported electromagnetic wave absorption counterparts. Moreover, its maximum effective absorption bandwidth is up to 4.7 GHz at the matching thickness of merely 1.8 mm. The excellent performance of the ultralight bimetal-based aerogels mainly derives from increased dielectric loss, better matching impedance and larger specific surface area. It could be believed our designed ultralight self-supported aerogels can be promising candidates for lightweight absorbers with strong attenuation abilities.

Ti3C2Tx has shown great potential in energy storage filed, but the restacking between Ti3C2Tx nanosheets seriously hampers the maximization of its capacitance. In this study, we rationally designed and synthesized porous Ti3C2Tx assemblies without any additive by introducing ice as spacers using a facile freeze-drying method. The porous Ti3C2Tx assemblies have a three-dimensional network structure, which consists of ultra large Ti3C2Tx lamellar walls and lots of macro- and mesopores. It has been proven that there are more -O groups on the surface of the porous Ti3C2Tx assemblies than the Ti3C2Tx film. The porous Ti3C2Tx assemblies deliver a maximum areal capacitance of 1668 mF/cm2 when the mass loading is 8.4 mg/cm2, an optimized specific capacitance of 247.2 F/g when the mass loading is 5.3 mg/cm2, and 87% capacitance retention over 10000 cycles. The symmetric solid-state supercapacitors based on the porous Ti3C2Tx assemblies show an areal capacitance of 355.8 mF/cm2, the maximum power density of 50 mW/cm2 and an outstanding flexibility under different deformation.

Exploring stable cycling electrode materials with high energy and power density is the key to accelerating the development and application of supercapacitors. Ti3 C2 Tx , which is the most investigated member of the family of two-dimensional layered transition-metal carbides, has attracted considerable attention, owing to its unique two-dimensional morphology, large interlayer spacing, outstanding metallic conductivity, abundant chemical surface, and ultrahigh volumetric capacitance. However, the inherent restacking tendency of ultrathin Ti3 C2 Tx sheets hinder its practical application. In this review, the synthetic methods and charge-storage mechanisms of Ti3 C2 Tx are stressed to provide clues for improving its electrochemical performance. Functionalization, including architectural construction, hybridization, and surface modification of the Ti3 C2 Tx sheets, to circumvent difficulties and application in supercapacitors is then summarized. Accordingly, the aim is to highlight the opportunities and challenges for Ti3 C2 Tx -based materials in practical applications in supercapacitors.

Lithium–sulfur batteries are the most promising next-generation power source thanks to their extremely high theoretical capacity. However, the uncontrollable lithium dendrite growth and side reactions between the polysulfides and electrolyte for the Li metal anode result in a short lifespan, rapid capacity decay, low Coulombic efficiency, and safety concerns, impeding their practical development. In this work, a novel dual-layered artificial SEI on the Li metal anode is reported, which consists of organic lithiated Nafion on the top and inorganic LixSiSy on the bottom. The flexible Nafion layer can not only maintain the structural integrity of the SEI, but also hinder the side reactions between soluble polysulfides and the lithium anode, while the rigid inorganic layer is beneficial for diffusion of Li ions within it and suppression of Li dendrite growth. Accordingly, the protected Li electrode can steadily withstand successive Li plating/stripping processes for over 1400 h at a current density of 1 mA cm−2. Li–S batteries with a LixSiSy/Nafion film coated Li anode exhibit better cycling stability (783 mA h g−1 after 300 cycles at 0.5C) and higher rate performance (789 mA h g−1 at 2.0C) than those with a bare Li anode. This work highlights the significance of rational manipulation of the interfacial properties of a working Li metal anode and provides fresh insights into achieving dendrite-free Li deposition behaviors and high-cyclability Li–S batteries.

Three-dimensional (3D) graphene-based structures have attracted much attention due to their unique physicochemical properties and potential applications in various fields. In this work, we develop a facile strategy for growing Co and Zn-contained nitrogen-doped carbon nanotubes on the graphene sheets for the absorption of electromagnetic wave (EMW). The as-fabricated 3D structures with a larger surface area have high electrical conductivities, abundant defects, numerous interfaces and porous feature, endowing them to excellent EMW absorption performance. The minimal reflection loss and efficient absorption bandwidth of the optimized 3D structure can reach to −47.31 dB and 4.01 GHz at a low thickness of merely 1.5 mm, respectively. Even at the thickness of 1.2–1.5 mm, the minimal reflection losses are less than −10 dB. Furthermore, the filler mass loading of the 3D structures is only 6 wt%, lower than those of most of the reported absorbers. Our results highlight the importance of 3D structures composed of graphene and nitrogen-doped carbon nanotubes to high-efficiency EMW absorption.

Lithium–sulfur (Li–S) batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability. The cathode with high sulfur areal loading is vital for the practical applications of Li–S batteries with very high energy density. However, the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases. Herein, we used diameters of 5.0 (D5) and 13.0 (D13) mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading (4.5 mg cm−2). The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large (D13) cathode. Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions, which results in inferior battery performance of the Li–S cell with large diameter cathode. This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading, carbon modified separators, organic electrolyte, and Li metal anode in a pouch cell, wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li–S battery.

Herein, we use reduced graphene oxide as a substrate and NiFe as a catalyst to fabricate three-dimensional (3D) nitrogen-doped carbon nanotube (NCNT)/reduced graphene oxide heteronanostructures (3D NiFe/N-GCTs). The 3D NiFe/N-GCTs are composed of two-dimensional (2D) reduced graphene oxide-supported one-dimensional (1D) NiFe nanoparticle-encapsulated NCNT arrays. The NCNTs exhibit bamboo-like shapes with the length and diameter of 3-10 μm and 15-45 nm, respectively. Besides integration of advantages of 1D and 2D nanomaterials, the 3D NiFe/N-GCT heteronanostructure possesses interconnected network structures, sufficient interfaces, numerous defects, hundreds of void spaces enclosed by bamboo joints and the walls of the NCNT in an individual carbon nanotube, and large surface areas, which can improve their dielectric losses toward electromagnetic wave. Thus, the 3D NiFe/N-GCTs show satisfied property toward electromagnetic wave absorption. Typically, the optimized 3D NiFe/N-GCT displays excellent minimal reflection loss (-40.3 dB) and outstanding efficient absorption bandwidth (4.5 GHz), outperforming most of the reported absorbers. Remarkably, the synthesis of 3D NiFe/N-GCTs only involves vacuum freeze-drying and subsequent thermal treatment process at a high temperature, and thus, the large-scale production of 3D NiFe/N-GCTs can be achieved in each batch, affording the possibility of the practical applications of the 3D NiFe/N-GCTs.

Lithium–sulfur batteries are attracting great attention due to their high theoretical capacity, low cost and environmental friendliness. However, the severe lithium polysulfides shuttling, self-discharge behavior and insulating end redox products (Li2S/Li2S2) remarkably hinder the performance. The cell configuration with an interlayer toward the cathode is an effective strategy to circumvent the above challenges. In this study, a carbon fibers/Ti3C2Tx interlayer is proposed to provide a physical shield and a strong chemical affinity to mitigate the polysulfides shuttling. The 3D cross-linked conductive networks of carbon fibers/Ti3C2Tx interlayers provide fast electron transfer channels and, thus, increase sulfur utilization and save “dead” sulfur. The dual effects of carbon fibers/Ti3C2Tx layers enable the Li–S cells with a high initial discharge capacity of 1380 mAhg−1 at a current density of 0.1 C and an ultralow capacity loss of 0.044% per cycle within 1000 cycles at 1 C. We found that the family of MXenes plays unique roles in immobilizing and converting the polysulfides. The design of a carbon fibers/Ti3C2Tx interlayer with dual effects paves the ways for improving the performance of battery systems that involve complex phase conversion reactions.

The rapid development of the portable and wearable electronics creates a high demand for better performance energy storage devices with high areal capacity as well as excellent flexibility. Herein, a free-standing Ti3C2/FeOOH quantum dots (QDs) hybrid film has been designed and synthesized by a simple electrostatic self-assembly, where amorphous FeOOH QDs not only act as pillars to prevent restacking of the Ti3C2 nanosheets but also provide considerable capacitance as active materials. The Ti3C2/FeOOH QDs hybrid film exhibits 2.3 times higher areal capacitance (485 mF cm−2) than the pristine Ti3C2 film and good cycle stability (94.8% retention over 5000 cycles) in neutral electrolyte. Moreover, an asymmetric device has been prepared by combining the hybrid film as negative electrode and MnO2 on carbon cloth as positive electrode, which operates at an output potential difference of 1.6 V. The device delivers the maximum energy density of 40 μW h cm−2 and the maximum power density of 8.2 mW cm−2 with 82% capacitance retention after 3000 cycles. The facile preparation process and excellent electrochemical properties of the free-standing Ti3C2/FeOOH QDs hybrid film make it a promising candidate for constructing high-performance flexible energy storage devices.

Most of metal−organic frameworks (MOFs) themselves have low electrical conductivities, leading to bad electromagnetic wave (EMW) absorption properties. Herein we found that the EMW absorption property of zeolitic imidazolate frameworks-8 (ZIF-8) particles was improved unexpectedly after coupling them with graphene sheets. Experimental results and theoretical calculations indicated that well-defined interfaces between ZIF-8 and the graphene sheets were crucial to the improvement of EMW absorption property. Our strategy presented here may open a new way for designing other MOFs based hybrids for high-performance EMW absorbers.

To solve the restacking of the Ti3C2Tx nanosheets and destroy of electrode microstructure during cycles and gain high-performance electrode for supercapacitors, Ti3C2Tx/PDA composite film electrode was rationally designed and successfully synthesized by one-step in situ polymerization of dopamine on the surface of the Ti3C2Tx nanosheets. The as-synthesized Ti3C2Tx/PDA composite electrode achieved a superior areal capacitance of 715 mF/cm2 at a scan rate of 2 mV/s and maintained 95.5% of initial capacitance after 10000 cycles, exhibiting long-term cycling stability. The areal capacitance can be enhanced to 3440 mF/cm2 when the mass loading increases to 13.6 mg/cm2. The improved electrochemical performance and outstanding electrochemical stability can be attributed to the effective suppressing the restacking of Ti3C2Tx sheets and increasing interlayer spacing by introducing PDA, which could be beneficial to expose more surface active sites, shorten the diffusion path of electrolyte ions, promote electron transport and fast Faradaic reaction. Our work opens new design space to develop the high performance negative electrode materials.

Superstructure design of a single-layer MoS2/C/Ti3C2Tx@C composite electrode is reported. Application of the composite materials as high performance electrode for lithium ion batteries is investigated. The composite materials are comprised of the SL-MoS2/C superstructure and Ti3C2Tx@C core-shell structure. The SL-MoS2/C superstructure with a nanoscopic/atomic interface could efficiently prevent undesirable surface reactions between the active materials and electrolyte. The cycling performance of active MoS2 can be greatly improved due to the incorporation of superstructure. The SL-MoS2/C/Ti3C2Tx@C composite electrode shows an ultralong cycle life and delivers a discharge capacity of 962 mAh g−1 at the current density of 0.1 A g−1. A high reversible capacity of 875 mAh g−1 is retained even after 1500 cycles at the current density of 1.0 A g−1.

The high intercalation capacitance of MXenes is attractive, but their performance as electrodes in supercapacitors is limited by mass transport when increasing the thickness and mass loading of the electrodes. Here, we report a combined experimental and computational study, through which we reveal the diffusion of hydrated ionic species at the interlayer spaces. We find that the cyclic voltammetry (CV) curves for the delaminated Ti3C2T x exhibit distinct features in acid (H2SO4) and alkaline (KOH) electrolytes. The calculated migration profiles of K+ and H+ using density functional theory, in the presence and absence of water, suggest that the intercalated water molecules stabilize the charged ions, facilitating their diffusion from two dimension to three dimension manifested by reduced activation barriers and movement pathways. In addition, we show that the diffusion of low and high concentrations of protons is significantly different; that is, protons of high concentrations can be adsorbed at both sides of the interlayer spaces, and water drives frequent proton hopping between stable adsorption sites as shown in the ab initio molecular dynamics simulations. The calculations can thus explain the varied capacitance and distorted CV curves when the experiments are conducted in acid and alkaline electrolytes. These results can provide guidance for improving the fast transport of ions and electrons in MXenes with high mass loading.

MXenes are two-dimensional transition metal carbides/nitrides, and they have shown exciting application prospects for electrochemical energy storage in the future owing to their hydrophilicity, metallic conductivity and surface redox reactions, which are crucial for high-capacitance and high-rate electrode materials. However, the strong tendency of adjacent MXene flakes to aggregate or self-restack under the van der Waals force limits the electrochemical performance of MXene-based electrodes for practical applications. In this study, we developed a simple and effective method to prepare Ti3C2Tx/PEDOT:PSS hybrid films via filtering the Ti3C2Tx/Clevios PH1000 compound inks, followed by H2SO4 treatment. H2SO4 treatment could remove part of the insulating PSS from the Ti3C2Tx/PEDOT:PSS hybrid film, resulting in significant conductivity enhancement of the composite. Furthermore, the conductive PEDOT not only acted as a pillar between Ti3C2Tx sheets to expose more electroactive surfaces and reduce ion diffusion pathways but also played a role as a conductive bridge to form multidimensional electronic transport channels for accelerating the electrochemical reaction process. As a result, the as-prepared H2SO4-treated Ti3C2Tx/PEDOT:PSS (Ti3C2Tx/P-100-H) hybrid film exhibited 4.5-fold increase in the specific surface area and high volumetric capacitance of 1065 F cm-3 at 2 mV s-1 with superior rate performance in 1 M H2SO4 electrolyte. Especially, we assembled an asymmetric supercapacitor (ASC) with excellent flexibility based on a Ti3C2Tx/P-100-H hybrid negative electrode and rGO film positive electrode, which delivered high energy density of 23 mW h cm-3 and high power density of 7659 mW cm-3. Moreover, a simple luminous band was designed and powered by our two ASCs in series. The outstanding volumetric electrochemical performance and energy density of the ASC based on the flexible Ti3C2Tx/P-100-H hybrid film electrode demonstrated its promising potential as a strong power source for small portable and wearable electronic devices.

High-performance multi-functional electrocatalysts are highly desirable for various energy storage and conversion devices. In this study, we report a one dimensional N-doped carbon nanostructure, containing Mo2C and Co nanoparticles encapsulated in nitrogen-doped graphene layers (Mo2C@NC/Co@NG) as a multi-functional electrocatalyst. The optimized Mo2C@NC/Co@NG exhibited high activities and stabilities towards oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The experimental results demonstrate that the high activities and stabilities of the multi-functional catalysts are ascribed to the synergistic effect between Mo2C, Co, and N dopants. Typically, the optimized Mo2C@NC/Co@NG catalyst delivered a HER current density of 10 mA cm−2 at a small overpotential of 142 mV. Furthermore, a rechargeable zinc–air battery with the optimized Mo2C@NC/Co@NG as OER and ORR bifunctional catalyst showed a high round-trip efficiency and robust cycling stability, superior to the battery assembled with the benchmarked mixture of Pt/C and IrO2 as the air electrode. This study provides a simple method to reasonably design and fabricate highly efficient and stable multi-functional catalysts for clean and sustainable energy storage and conversion devices.

Lithium–sulfur (Li–S) batteries with a high theoretical energy density based on multi-electron redox reactions were strongly considered. The lithium disulfide/sulfide (Li2S2/Li2S, denoted as Li2S1/2) precipitation is critical to achieve high sulfur utilization. However, the kinetic effect on Li2S1/2 precipitation in a working battery has been rarely investigated. Herein, the current-density-dependent Li2S1/2 nucleation/growth was explored and such a dependence served as the guiding principle for the construction of high-sulfur-loading/content Li–S batteries. Generally, the Li2S1/2 nucleation density is proportional to two-third the power of the current density and the shift from a high to low current density alters the Li2S1/2 precipitation pathway from surface deposition to solution-mediated growth. The in-solution growth rate was found to be restricted by the mobilities of polysulfide intermediates and Li2S1/2 in conventional ether electrolytes. The rationalized guideline directed the design of a lightweight, high-surface-area, and open-pore conductive framework for sulfur cathodes, which enabled an extremely high sulfur content of 93.4 wt% in the whole electrode and a high capacity (1269 mA h g−1). The present work affords a kinetic understanding of the liquid–solid conversion in working Li–S batteries and optimization schemes for practical operation parameters.

In this work, we use a metal–organic framework and layered double hydroxide nanosheets as precursors to grow transition-metal nanoparticle-encapsulated nitrogen-doped carbon nanotubes on ultrathin graphene sheets. The as-fabricated samples exhibit three-dimensional structures with high electrical conductivities, abundant defects, multiple interfaces and nitrogen dopants. As applied for the attenuation of electromagnetic energy, the optimized 3D architecture with CoNi bimetal nanoparticles exhibits excellent attenuation properties of electromagnetic energy even at a thin thickness of 1.5 mm and a low filling ratio of 10 wt% in a paraffin matrix, superior to those of single-metal based 3D architectures and most reported materials. The experimental results demonstrate that the dielectric loss and the impedance matching characteristic can be modulated by adjusting metal compositions, which are responsible for the difference of the 3D architectures in EME attenuation properties. Our strategy opens a new way for lightweight materials for the attenuation of electromagnetic energy.

Nitrogen-doped carbon sheets containing Fe 3 C nanoparticles encapsulated in nitrogen-doped graphene shells are fabricated through heating the mixture of urea and ferric acetylacetonate and the subsequent treatment in hot acid solution. The nitrogen-doped carbon sheets have a lateral length ranging from hundred nanometers to several micrometers, while the Fe 3 C nanoparticles encapsulated in nitrogen-doped graphene have a diameter of approximately 60 nm. The nitrogen-doped carbon sheets exhibit excellent electromagnetic wave absorption property. Typically, the optimal sample has the effective absorption bandwidth of 6.0 GHz at the absorber thicknesses of only 2.0 mm, favorably comparable to those of the magnetic absorbers reported previously. The excellent electromagnetic wave absorption property of nitrogen-doped carbon sheets containing Fe 3 C nanocapsules encapsulated in the nitrogen-doped graphene shells can be explained by their better impedance matching character and enhanced dielectric loss.

The application of lithium metal anodes for practical batteries is still impeded by safety issues and low Coulombic efficiency caused mainly by the uncontrollable growth of lithium dendrites. Herein, two types of free-standing nitrogen-doped amorphous Zn-carbon multichannel fibers are synthesized as multifunctional hosts for lithium accommodation. The 3D macroporous structures endow effectively reduced local current density, and the lithiophilic nitrogen-doped carbon and functional Zn nanoparticles serve as preferred deposition sites with low nucleation barriers to guide uniform lithium deposition. As a result, the developed anodes exhibit remarkable electrochemical properties in terms of high Coulombic efficiency for more than 500 cycles at various current densities from 1 to 5 mA cm-2 , and symmetric cells show long-term cycling duration over 2000 h. Moreover, full cells based on the developed anode and a LiFePO4 cathode also demonstrate superior rate capability and stable cycle life. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version X.W.L. acknowledges the funding support from the National Research Foundation (NRF) of Singapore via the NRF investigatorship (NRF-NRFI2016-04), and Ministry of Education of Singapore via the AcRF Tier-1 grant (RG3/20). X.T.Z. acknowledges the funding support from National Natural Science Foundation of China (51772069).

Diluted magnetic semiconductors (DMSs) have traditionally been employed to implement spin-based quantum computing and quantum information processing. However, their low Curie temperature is a major hurdle in their use in this field, which creates the necessity for wide bandgap DMSs operating at room temperature. In view of this, a single-electron transistor (SET) with a global back-gate was built using a wide bandgap ZnO nanobelt (NB). Clear Coulomb oscillations were observed at 4.2 K. The periodicity of the Coulomb diamonds indicates that the Coulomb oscillations arise from single quantum dots of uniform size, whereas quasi-periodic Coulomb diamonds correspond to the contribution of multi-dots present in the ZnO NB. By applying an AC signal to the global back-gate across a Coulomb peak with varying frequencies, single-electron pumping was observed; the increase in current was equal to the production of electron charge and frequency. The current accuracy of about 1% for both single- and double-electron pumping was achieved at a high frequency of 25 MHz. This accurate single-electron pumping makes the ZnO NB SET suitable for single-spin injection and detection, which has great potential for applications in quantum information technology.

Larger-scale usage of the clean energies requires advanced energy storage and conversion techniques. Overall water splitting and zinc air systems are promising energy conversion and storage means, but need high-performance, low-cost, and highly stable bifunctional electrocatalysts to hydrogen evolution/oxygen evolution reactions (HER/OER) and OER/oxygen reduction reactions (ORR), respectively. Herein we develop a facile method to fabricate CoMn double hydroxide (DH) hollow spheres as high-performance trifunctional electrocatalysts for overall water splitting and zinc-air battery. The outmost surfaces of the CoMn DH hollow spheres are composed of ultrathin nanosheets with a thickness of approximately 2.5 nm. Owing to the hollow and ultrathin features, CoMn DH hollow spheres exhibit excellent activities and robust stabilities toward HER, OER, and ORR. The overall water electrolyzer assembled with the CoMn DH hollow spheres can drive a current density of 10 mA cm–2 at an overpotential of merely 420 mV in 1.0...

Electrochemical water splitting is an efficient way for large-scale production of clean hydrogen fuel. However, high overpotential is required to catalyzing oxygen evolution reaction (OER). Here we fabricate self-supported CoMn-LDH nanosheets with a thickness of approximately 1.9 nm on carbon fiber cloth through electrodeposition method within 50 s. The self-supported, binder-free anodes exhibit excellent OER performance with an overpotential of 258 mV at 10 mA cm−2 in 0.1 M KOH solution, remarkably lower than those of Co and Mn single counterparts, and the-state-of-the-art IrO2 catalyst. Furthermore, self-supported, binder-free anodes exhibit robust stability for OER with a negligible current loss even at a high current density (>370 mA cm−2) over 15 h. Flexible and bendable measurements indicate no obvious degradation in the OER performance of the anode even as being bended to 180°. Moreover, the water electrolysis with the CoMn-LDH/CFC as anode and Pt/C/CFC as cathode only needs a cell voltage of 1.54 V to deliver the current density of 10 mA cm−2 in 0.1 M KOH solution. Our experimental results demonstrate that the electron interaction between Mn and Co, increased electrochemical active area and decreased charge-transfer resistance contribute to the enhancement of the optimized anode in OER performance.

To prevent restacking of the Ti 3 C 2 T x layers, the Ti 3 C 2 T x -foam has been successfully synthesized through thermal treatment of Ti 3 C 2 T x -film with the hydrazine monohydrate. The interconnected porous structure of Ti 3 C 2 T x -foam could effectively reduce the restacking of the Ti 3 C 2 T x sheets and shorten the diffusion path of ions and accelerate the intercalation/de-intercalation of ions. The Ti 3 C 2 T x -foam-80 used as free-standing electrode achieves a high areal capacitance of 271.2 mF/cm 2 (122.7 F/g) at a scan rate of 5 mV/s in 1 M KOH electrolyte. It also exhibited a high capability rate of 65.5% from 5 mV/s to 100 mV/s and good cycle life with 88.7% retention of its initial after 10,000 cycles at a scan rate of 50 mV/s.

Magnetic metal nanostructures have exhibited good electromagnetic wave (EMW) absorption properties. However, the surface of the nanostructures is easily oxidized upon exposure to air, leading to the bad stability of the EMW absorption properties. We use metal-organic framework structure as a template to fabricate hollow N-doped carbon polyhedron containing CoNi alloy nanoparticles embedded within N-doped graphene (CoNi@NG-NCPs). The atomic ratio of Co/Ni can be tuned from 1:0.54 to 1:0.91 in the hollow CoNi@NG-NCPs. Experimental results demonstrate that the EMW absorption properties of the CoNi@NG-NCPs can be improved through the Ni introduction and increased with an increase of the Ni content. Typically, the minimal reflection loss of the optimal CoNi@NG-NCP can reach -24.03 dB and the effective absorption bandwidth (reflection loss below -10 dB) is as large as 4.32 GHz at the thickness of 2.5 mm. Furthermore, our CoNi@NG-NCPs exhibit favorably comparable or superior EMW absorption properties to other magnetic absorbers. In addition, because the CoNi alloy nanoparticles are coated with N-doped graphene layers, their surface oxidation behavior can be efficiently limited. The mechanism of the enhanced EMW absorption property is relevant to the enhanced dielectric loss and better impedance matching characteristic caused by the Ni incorporation.

Designing noble-metal-free and highly active bifunctional electrocatalysts for overall water splitting is extremely desirable. Herein, we apply a facile method to fabricate cobalt nitride porous nanowires with a length of 7 μm and a diameter of 135 nm on carbon cloth (CC) as a bifunctional electrocatalyst for overall water splitting. The self-supported cobalt nitride porous nanowire arrays exhibit superior catalytic activities with a current density of 10 mA cm-2 at an overpotential of 97 mV for hydrogen evolution reaction and at an overpotential of 251 mV for oxygen evolution reaction. The alkaline water electrolyzer with the self-supported porous nanowire arrays as cathode and anode requires a cell voltage of 1.587 V to achieve a current density of 10 mA cm−2 and shows long-term stability at the high current density(∼360 mA cm−2) over 37 h, favorably comparable to the integrated performance of commercial Pt and IrO2.

It is a confused problem in the literature that the c-axis value of Ti3C2 MXene changes with the synthesis procedure, but the part of the surface structures that plays the role of pillar to support the Ti3C2 layers and their variation rules remain controversial. In this work, we develop the structure models and formation mechanisms of Ti3C2Tx based on the density functional theory calculations and experimental results. While the c-axis values of the samples vary from about 1.9 to 2.9 nm, the corresponding pillars are determined by different distributions and proportions of the H-containing groups. The proportions of the H-containing groups that determine the c-axis value are formulated as the functions of the interlayer space, which can be used to quantitatively clarify the changes of the surface functional groups after the samples experiencing different treatments. The results can facilitate the in situ detections of the surface structures of MXenes during different treatments or electrochemical processes.

MXene has attracted significant attention as a promising electrode material for energy storage applications. In this study, the energy storage properties of Nbn+1Cn (n = 1 or 2), as a member of the MXene family, are investigated by using the first-principle density-functional theory. Bare Nb2C and Nb3C2 systems show an extremely high theoretical capacitance of Li atoms. It is determined that the surface termination has a considerable impact on the energy storage properties. The F- or O-terminated surfaces promote a charge transfer between the adatom and the surface. However, these terminations obviously reduce the electronic conductivity and the rate performance in the charge/discharge process. Moreover, the F- and OH-functional groups on the Nbn+1Cn surfaces can be removed through metal atom absorption. Our findings can be useful in designing MXene-based electrode materials for energy storage applications.

Two-dimensional titanium carbide has gained considerable attention in recent years as an electrode material for supercapacitors due to its high melting point, good electrical conductivity, hydrophilicity and large electrochemically active surfaces. However, the irreversible restacking during synthesis restricts its development and practical applications. Here, Ti 3 C 2 T x /SCNT self-assembled composite electrodes were rationally designed and successfully synthesized by introducing single-walled carbon nanotubes (SCNTs) as interlayer spacers to decrease the restacking of the Ti 3 C 2 T x sheets during the synthesis process. SCNTs can not only increase the specific surface area as well as the interlayer space of the Ti 3 C 2 T x electrode, but also increase the accessible capability of electrolyte ions, and thus it improved the electrochemical performance of the electrode. The as-prepared Ti 3 C 2 T x /SCNT self-assembled composite electrode achieved a high areal capacitance of 220 mF/cm 2 (314 F/cm 3 ) and a remarkable capacitance retention of 95% after 10,000 cycles.

Mesoporous TiO2 spheres with high crystallinity and large specific surface area were facilely prepared via sol–gel and solvothermal methods. By tuning the time and temperature of the solvothermal process, the specific surface area and pore size of TiO2 spheres were fine-controlled without any additives. Compared with the dye-sensitized solar cell (DSC) based on the commercial P25 nanoparticles, the dye-sensitized solar cell employing optimized TiO2 spheres achieves an excellent efficiency of 10.3%, due to the outstanding dye-loading and light-scattering abilities as well as attenuated charge recombination. Furthermore, an impressive efficiency of 11.2% can be obtained after TiCl4 post-treatment. More importantly, in combination with a single-layer TiO2 film composed of mesoporous spheres and low-volatility electrolyte, the DSC exhibits high efficiency and long-term durability.

We developed a facile method for the growth of hollow structured NiCo2O4 nanoparticles on a graphene sheet (NiCo2O4-h/G). The hollow NiCo2O4 nanoparticles have an average diameter of approximately 10.0 nm and a shell thickness of merely 2.5 nm. The NiCo2O4-h/G hybrid exhibited excellent electromagnetic wave absorption with minimal reflection loss below −20 dB at absorber thickness ranging from 2.0 to 5.0 mm, outperforming the solid NiCo2O4 nanoparticles on the graphene sheet. Remarkably, even for a thickness as small as 1.5 mm, the efficient absorption bandwidth and the minimal reflection loss of the hybrid can reach 2.6 GHz and −20.3 dB, respectively. Experimental results and theoretical calculations indicate that the void space in the hollow NiCo2O4 nanoparticles plays a crucial role in the excellent electromagnetic wave absorption property, which greatly increases the dielectric loss and impedance matching characteristics. Our results demonstrate that growing the hollow nanoparticles on a graphene sheet is an efficient way to produce high-performance electromagnetic wave absorbers.

Two-dimensional titanium carbide as a novel electrode material has been widely researched in the field of energy storage in recent years. However, the restacking of Ti3C2Tx nanosheets is still a challenge, which largely restricts their development. Here, we employ the 3D architecture of a Ti3C2Tx aerogel to restrict the restacking of 2D Ti3C2Tx nanosheets. This special structure can not only effectively reduce the restacking of 2D materials, but also accelerate the transport of electrolyte ions in the electrode. The as-prepared Ti3C2Tx aerogel possessed a large special surface area of 108 m2 g−1 and achieved a special capacitance of 349 F g−1 which is retained even at a high scan rate of 2000 mV s−1 in the 3 M H2SO4 electrolyte, indicating an ultrahigh rate capability. Moreover, at a higher current density of 20 A g−1, 90% of the initial capacitance is also retained after 20 000 charging–discharging cycles, revealing an excellent cycling stability. Furthermore, the mechanism of charge storage was investigated.

PbSe nanotubes (NTs) were synthesized through a low cost, facile and green hydrothermal route in combination with the assistance of ascorbic acid. In the hydrothermal reaction process, Se nanowires were not only used as templates, but also as a Se ion source to provide Se precursors for the growth of PbSe NTs. The prepared tubular crystals with a cubic structure have a length of 1–6 μm and an average diameter of ∼120 nm. Experimental results show that the amount of ascorbic acid and Pb2+ concentration play important roles in the formation of PbSe NTs, and a possible growth mechanism of PbSe NTs has also been presented. Additionally, the photocatalytic activity of the PbSe NTs was investigated and the results establish that PbSe NTs, in the presence of H2O2, showed a high photodegradation efficiency for methylene blue (MB). A probable photocatalytic mechanism for PbSe NTs is also discussed.

CoFe2O4 hollow nanoparticles with an average diameter and shell thickness of about 9.0 nm and 3.0 nm, respectively, were grown on graphene sheets. The hybrid exhibited excellent electromagnetic wave absorption properties with all of the minimal reflection losses below −10 dB at a thickness of 1.5–5.0 mm, superior to the hybrid based on CoFe2O4 solid nanoparticles and recently reported absorbers. Our results open a novel way for fabrication of hollow nanoparticles on graphene sheets for high-performance electromagnetic wave absorbers.

Herein, ultra-small NiFe2O4 hollow particles, with the diameter and wall thickness of only 6 and 1.8 nm, respectively, were anchored on a graphene surface based on the nanoscale Kirkendall effect. The hybrid exhibits an excellent electromagnetic wave absorption property, comparable or superior to that of most reported absorbers. Our strategy may open a way to grow ultra-small hollow particles on graphene for applications in many fields such as eletromagnetic wave absorption and energy storage and conversion.

Three-dimensional (3D) MoS2@carbon fibers (CFs) hierarchical architectures are successfully synthesized via a simple hydrothermal method and subsequent annealing. MoS2 nanoflakes are grown on the twine carbon fibers of the carbonized waste cotton cloth. The twine CFs can provide a short diffusion path for ions in electrolyte, enhance the specific surface area, and improve the conductivity of the 3D MoS2@CFs hierarchical architectures with high mass loading of 4.4mgcm-2. The 3D MoS2@CFs hierarchical architectures as the electrode material can achieve a high reversible areal capacity (5.2mAhcm-2 at 2.5mAcm-2) and exhibit an excellent rate performance. In addition, CFs are prepared by simply carbonizing the waste cotton and then used as carbon source, which is low-cost and eco-friendly. We also found that the Mo nanoparticles produced during the charge/discharge process exist in the hierarchical architectures during cycling and can improve the conductivity of the entire system as well as the cycling stability. Therefore, MoS2@CFs nanocomposites as electrode materials manifest a significant application potential for high-performance Li-ion batteries.

Large-area ZnO/Cu2O heterojunction have been successfully synthesized on Cu foil through a simple two-step solution method at near room temperature. The field emission scanning electron microscopy characterization indicates that the morphology of as-prepared Cu2O film grown on Cu foil is octahedral structure with diameter of ∼450 nm and ZnO is nanorod arrays structure with diameter of ∼150 nm. The current–voltage measurement of ZnO/Cu2O heterojunction shows a typical rectifying characteristics. Moreover, the photocatalytic test indicates that ZnO/Cu2O heterojunction exhibits high photocatalytic efficient for degradation of congo red dyes. The possible photocatalytic mechanism of ZnO/Cu2O heterojunction is also presented.

Lithium-sulfur batteries suffer from poor cycling stability and inferior rate capability, mainly caused by low conductivity and lithium polysulfide dissolution. To tackle these problems, this work demonstrates that Ti3C2Tx "clay", synthesized by selectively extracting the Al layers from the Ti3AlC2 phases with a mixture of HCl and LiF, is an effective host material for sulfur cathodes. To further enhance the rate performance and cycling stability of S/Ti3C2Tx composites, a single-walled carbon nanotube thin film was prepared by a simple vacuum filtration method and inserted between the cathode and the separator as an interlayer for Li-S batteries. The S/Ti3C2Tx composite with an interlayer could deliver a high initial discharge capacity of 1458 mA h g-1 at a current density of 0.1 A g-1 and an ultralow capacity decay of 0.04% per cycle at 0.8 A g-1 for over 1500 cycles was achieved. More importantly, a reversible capacity of 608 mA h g-1 was obtained at a high current density of 8.2 A g-1 (≈5C), demonstrating superior rate capability. These results suggest that the S/Ti3C2Tx composite is a promising sulfur cathode material and the introduction of the interlayer will pave the way for the future development and design of high-rate with long-cycle Li-S batteries.

Ti3C2Tx is promising negative electrode materials for asymmetric supercapacitor (ASC). The Ti3C2Tx sheets are obtained by etching Ti3AlC2 powders in the mixture solution of HCl and LiF, then vacuum filtrated to achieve a free-standing Ti3C2Tx-paper. The electrochemical performance of Ti3C2Tx-paper was measured and a high volumetric capacitance of 295.4 F cm−3 was achieved. Meanwhile, it exhibited a high capability rate of 79.7% from 2 mV s−1 to 100 mV s−1 and long cycle life with 94.4% retention of its initial after charged and discharged for 15000 cycles at a current density of 10 A g−1. ASC devices were fabricated using Ti3C2Tx-paper as negative electrode and carbonized filter paper as positive electrode. The energy density and power density of ASC device are 4.5 Wh kg−1 and 1.3 kW kg−1, respectively. The application of the device has been demonstrated by lighting red light emitting diode, endowing prospect of the Ti3C2Tx-paper as negative electrode for supercapacitors.

Anti-EGFR nanobodies have been successfully applied as antitumor moieties in the photodynamic therapy and drug delivery systems. But the yields of nanobodies were still limited due to the volumetric capacity of the periplasmic compartments and inclusion bodies of Escherichia coli. A comparative study of Pichia pastoris and Escherichia coli was done through characterizing their products. Nanobody 7D12 and 7D12-9G8 were successfully expressed in Pichia pastoris with 6–13.6-fold higher yield. Both two types of nanobodies had internalization ability to be developed as antitumor moieties.

The boundary between quantum capacitance and pseudocapacitance is blurred due to their similarity in electronic populations. Here we propose the rules to classify the contributions of quantum capacitance and pseudocapacitance and their effects on the intrinsic ion transport kinetics based on the applied voltages and electronic structures. Systems including graphite, LiFePO4, LiTiS2, LiCoO2, and Ti3C2Tx MXene are employed to illustrate their different intrinsic kinetics according to the classifications based on the density functional theory calculations and the reported experimental measurements. These results can facilitate the step to screen the electrode materials with different kinetics through calculations.

Novel 3D Ti 3 C 2 aerogel has been first synthesized by a simple EDA-assisted self-assembly process. Its inside are channels and pores structure. The interconnected aerogel structure could efficiently restrain restacking of Ti 3 C 2 flakes. Thus, it exhibits a large specific surface area as high as 176.3 m 2 g −1 . The electrochemical performances have been measured. The Ti 3 C 2 aerogel achieves a quite high areal capacitance of 1012.5 mF cm −2 for the mass loading of 15 mg at a scan rate of 2 mV s −1 in 1 M KOH electrolyte. An asymmetric supercapacitor (ASC) has been assembled by using the Ti 3 C 2 aerogel electrode as the negative electrode and electrospinning carbon nanofiber film as the positive electrode. The device can deliver a high energy density of 120.0 μWh cm −2 and a maximum power density of 26123 μW cm −2 . A lamp panel with nineteen red light-emitting diodes has been powered by two ASCs in series.