Red Phosphorus Anchored on Nitrogen-Doped Carbon Bubble-Carbon Nanotube Network for Highly Stable and Fast-Charging Lithium-Ion Batteries.

A nitrogen-doped carbon bubble-carbon nanotube@red phosphorus (N-CBCNT@rP) network composite is fabricated, featuring an rP film embedded in a highly N-doped CBCNT network with hierarchical pores of different sizes and interior void spaces. Highly N-doped CBCNT with an optimized structure is utilized to achieve an ultrahigh rP content of 53 wt% in the N-CBCNT@rP composite by the NP bond, which shows a record rP content for rP-carbon composites by the vaporization-condensation process. When tested as an anode for lithium-ion batteries, the N-CBCNT@rP composite exhibits an ultrahigh initial Coulombic efficiency of 87.5%, high specific capacity, outstanding rate performance, and superior cycling stability at a high current density (capacity decay of 0.011% per cycle over 1500 cycles at 5 A g-1 ), which is the lowest capacity fading rate of those previously reported for rP-based electrodes. The superior lithium-ion storage performance of the N-CBCNT@rP composite electrode is primarily attributed to its structure. The 3D hierarchical conducting network of the N-CBCNT@rP composite with abundant N-P bonds endows the entire electrode with maximized conductivity for superior ion and electron transfer kinetics. Moreover, N-CBCNT networks with hierarchical pores of different sizes can fix the location of rP, prevent agglomeration, and avoid volume expansion of rP.

TiO2 Nanotubes Array on Carbon Cloth as a Flexibility Anode for Sodium-Ion Batteries.

In this work, three-dimensional (3D) TiO2 nanotubes (NTs) on carbon cloth (CC) (TiO2 NTs/CC) were synthesized by a method involving formation of a ZnO@TiO2 nanorod (NRs) on CC (ZnO@TiO2 NRs/CC) structure and a subsequent chemical etching process for ZnO NRs template. The 3D TiO2 NTs/CC were applied as flexible anodes for sodium ion batteries (SIBs). The TiO2 NTs/CC yielded high specific capacity and good cycling stability, superior to that of some reported TiO2 nanocomposites. The TiO2 NTs/CC delivered a reversible capacity of 260 mA·h·g-1 and 85.1% capacity retention over 150 cycles at current density of 0.25 C (1 C = 335 mA·g-1). It also exhibited high rate capacity of 200 mA·h·g-1 at 0.5 C. Even at a high rate of 1.0 C, the TiO2 NTs/CC can still maintain a high capacity of 100 mA·h·g-1. Moreover, it was observed that the electrochemical performance for the TiO2 NTs/CC was much better than that (150 mA·h·g-1 for up to 150 cycles) of a solid TiO2 NRs/CC counterpart, which also demonstrated the capacity enhancement and good cycling stability.

Stabilizing Lithium-Sulfur Batteries through Control of Sulfur Aggregation and Polysulfide Dissolution.

Lithium-sulfur (Li-S) batteries are investigated intensively as a promising large-scale energy storage system owing to their high theoretical energy density. However, the application of Li-S batteries is prevented by a series of primary problems, including low electronic conductivity, volumetric fluctuation, poor loading of sulfur, and shuttle effect caused by soluble lithium polysulfides. Here, a novel composite structure of sulfur nanoparticles attached to porous-carbon nanotube (p-CNT) encapsulated by hollow MnO2 nanoflakes film to form p-CNT@Void@MnO2 /S composite structures is reported. Benefiting from p-CNTs and sponge-like MnO2 nanoflake film, p-CNT@Void@MnO2 /S provides highly efficient pathways for the fast electron/ion transfer, fixes sulfur and Li2 S aggregation efficiently, and prevents polysulfide dissolution during cycling. Besides, the additional void inside p-CNT@Void@MnO2 /S composite structure provides sufficient free space for the expansion of encapsulated sulfur nanoparticles. The special material composition and structural design of p-CNT@Void@MnO2 /S composite structure with a high sulfur content endow the composite high capacity, high Coulombic efficiency, and an excellent cycling stability. The capacity of p-CNT@Void@MnO2 /S electrode is ≈599.1 mA h g-1 for the fourth cycle and ≈526.1 mA h g-1 after 100 cycles, corresponding to a capacity retention of ≈87.8% at a high current density of 1.0 C.

Surface Coating Constraint Induced Anisotropic Swelling of Silicon in Si-Void@SiO x Nanowire Anode for Lithium-Ion Batteries.

Here a simple and an environmentally friendly approach is developed for the fabrication of Si-void@SiOx nanowires of a high-capacity Li-ion anode material. The outer surface of the robust SiOx backbone and the inside void structure in Si-void@SiOx nanowires appropriately suppress the volume expansion and lead to anisotropic swelling morphologies of Si nanowires during lithiation/delithiation, which is first demonstrated by the in situ lithiation process. Remarkably, the Si-void@SiOx nanowire electrode exhibits excellent overall lithium-storage performance, including high specific capacity, high rate property, and excellent cycling stability. A reversible capacity of 1981 mAh g-1 is obtained in the fourth cycle, and the capacity is maintained at 2197 mAh g-1 after 200 cycles at a current density of 0.5 C. The outstanding overall properties of the Si-void@SiOx nanowire composite make it a promising anode material of lithium-ion batteries for the power-intensive energy storage applications.

Molten Au/Ge alloy migration in Ge nanowires.

Herein, we report time-resolved in situ transmission electron microscopy observation of Au particle melting at a Ge nanowire tip, subsequent forming of Au/Ge alloy liquid, and its migrating within the Ge nanowire. The migration direction and position of the Au/Ge liquid can be controlled by the applied voltage and the migration speed shows a linear deceleration in the nanowire. In a migration model proposed, the relevant dynamic mechanisms (electromigration, thermodiffusion, and viscous force, etc.) are discussed in detail. This work associated with the liquid mass transport in the solid nanowires should provide new insights into the crystal growth, interface engineering, and fabrication of the heterogeneous nanostructure-based devices.

F-doped NiCo2O4@CoMoO4 as an advanced electrode for aqueous Zn-ion batteries.

Heterostructure engineering and element doping is a trustworthy route to attain outstanding aqueous Zn-ion battery electrode materials. Herein, we develop a new type of F-doped NiCo2O4@CoMoO4 hierarchical nanostructure with abundant oxygen vacancies for aqueous Zn-ion batteries. The NiCo2O4@F-CoMoO4 electrodes exhibit an excellent specific capacity of 402 mA h g-1 at 1 A g-1. The assembled NiCo2O4@F-CoMoO4//Zn battery has an excellent specific capacity of 328 mA h g-1 at 2 A g-1, and a high energy density of 544.6 W h kg-1 at a power density of 0.923 kW kg-1.

Monodisperse functionalized GO for high-performance sensing and bioimaging of Cu2+ through synergistic enhancement effect.

The metal ion fluorescence probes based on chemical reactions triggered by specific metal ions is characterized by high selectivity. However, they are also subject to inherent limitations, such as easy aggregation under water solution, poor optical stability, and long response time. In order to solve these problems, a simple and effective method was studied. The specific design is as follows. Fluorescence probe RACD is assembled onto a single layer graphene oxide (GO) via π-π interaction and hydrogen bonding to prepare RACD functionlized graphene oxide RACD/GO. The experimental results show that the resulting RACD/GO possesses very well monodispersion, hydrophilicity and photostability, particularly reduce the aggregation degree of RACD owing to π-π effect. Simultaneously, it was found that due to the strong synergy between GO and RACD, the response time, selectivity, anti-interference ability, detection sensitivity, detection limit and bioimaging ability of RACD/GO were significantly improved compared with RACD. The resulting RACD/GO not only possesses very well photostability, multiple repeated cycles, but also have been triumphantly put into the monitoring Cu2+ of environmental water, sewage, cells and zebrafish specimens in practice. The detection limit is as low as 1.76 nM, and the correlation coefficient is 0.9998.

Structure-tunable Mn3O4-Fe3O4@C hybrids for high-performance supercapacitor.

Controlling the morphology and structure of nanomaterials is of great importance for enhancing the electrochemical properties. In the paper, Mn3O4-Fe3O4@C hybrids with different architectures were synthesized by incubation of electrospun FeOx-containing carbon fiber (Fe-CNF) in KMnO4 solution followed by annealing. The presence of FeOx on the CNF plays a vital role in determining the morphology and structure of the final hybrids, and the Mn3O4-Fe3O4@C hybrids with half-tube, tube and oolite-filled fibers are formed conveniently by tuning Fe content in the carbon fiber precursor. The good conductivity of fiber and various redox states of Mn and Fe afford the facile charge transfer and excellent reversible redox properties, thus enhancing the capacitor performance. The oolite-filled Mn3O4-Fe3O4@C with tubular structure exhibited a high specific capacitance of 178 F g-1 at a discharge rate of 1 A g-1. This capacitor electrode has an excellent cyclic stability with 95% capacitance retention after 1000 cycles at 3 A g-1. This work provides a very simple strategy to tune the unique nanostructures of metal oxide on Fe-CNF for high-performance supercapacitor application in the future.

Engineering oxygen vacancies and surface chemical reconstruction of MOF-derived hierarchical CoO/Ni2P-Co2P nanosheet arrays for advanced aqueous zinc-ion batteries.

Aqueous zinc-ion batteries (ZIBs) are emerging as promising alternatives among various energy storage devices. However, the lack of research on cathode materials with both high capacity and electrochemical stability restricts widespread applications of ZIBs. Herein, surface chemical reconstruction and partial phosphorization strategies are employed to synthesize MOF-derived hierarchical CoO/Ni2P-Co2P nanosheet arrays on Ni foam substrates as cathodes for ZIBs. The unique hierarchical nanostructure and multiple components with exposed surfaces and rich oxygen vacancies accelerate charge transfer and ion diffusion, expose more active sites, and promote the accessibility between the active materials and electrolyte. The oxide/phosphide composites obtained by novel partial phosphorization achieve a common improvement of performance and stability. As expected, the CoO/Ni2P-Co2P electrode delivers a high specific capacity (370.4 mA h g-1 at 3 A g-1) and excellent rate performance (63.3% retention after a six-fold increase in the current density). Moreover, when employed as the cathode of the CoO/Ni2P-Co2P-30//Zn battery, the assembled battery exhibits a superior specific capacity (322.8 mA h g-1 at 2 A g-1), a long cycle life (104.9% retention after 6000 cycles), a favorable energy density (547.5 W h kg-1) and power density (9.7 kW kg-1). Therefore, this study provides a suitable candidate which meets the requirements of high-performance cathode materials for ZIBs.

Interface engineering of Co3O4 nanowire arrays with ultrafine NiO nanowires for high-performance rechargeable alkaline batteries.

Interface engineering multi-component core-shell nanostructures with highly efficient and reversible faradaic reactions for energy conversion storage devices is still a challenge. Here, Co3O4 nanowires@NiO ultrafine nanowires on Ni foam were well fabricated via coating the NiO ultrafine nanowires on porous Co3O4 nanowire arrays. The combination of structural and compositional advantages endows the Co3O4@NiO core-shell composites with excellent electrochemical performance, such as a favorable specific capacity of 0.71 mA h cm-2 at 3 mA cm-2, excellent rate capability and 85% retention rate up to 10,000 cycles. Rechargeable alkaline batteries with the Co3O4@NiO core-shell composites and AC as cathode and anode, respectively, had a high specific capacity of 0.51 mA h cm-2 and stable cycling ability (81% retention after 5000 cycles). The hierarchical core-shell heterostructure electrode exhibits excellent electrochemical performance, making it a very promising material for next-generation energy storage device applications.

Structure-designed synthesis of hierarchical NiCo2O4@NiO composites for high-performance supercapacitors.

The design of multicomponent electrode materials is attractive for advanced supercapacitors due to synergistic and multifunctional effects among different active materials. We reported here a structure-designed synthesis strategy to controllably fabricate hierarchical NiCo2O4@NiO composites on carbon fiber paper. The hierarchical structure with NiCo2O4 core and NiO shell provided more active sites for ion transportation and storage to improve utilization rate of electrode materials, enhancing the specific capacitance and rate performance. As an ideal electrode material for supercapacitors, the NiCo2O4@NiO electrode exhibit high specific capacitance (1188 F/g at 2 A/g), excellent rate capability with ∼85% capacitance retained at 10 A/g, and compelling cycling performance (∼106.8% of the initial capacitance retention over 7000 cycles). The present work demonstrated a structure-designed strategy to construct high-performance multicomponent electrode materials for supercapacitors.

Enhancing the electrochemical performance of nickel cobalt sulfides hollow nanospheres by structural modulation for asymmetric supercapacitors.

The development of nickel cobalt sulfides electrodes with excellent electrochemical performance is important for supercapacitor applications. In this study, we constructed well-defined hierarchical nanosheet-built NiCo2S4/Co9S8 hollow nanospheres based on morphology and structural engineering. A combination of structural and compositional advantages endowed NiCo2S4/Co9S8 hollow nanospheres with enhanced electrochemical performance with favorable capacitance of 1008 F g-1 at 1 A g-1, exceeding that of single-component NiS (616 F g-1 at 1 A g-1) and Co3S4 (430 F g-1 at 1 A g-1). Furthermore, an assembled asymmetric supercapacitor (ASC) comprising NiCo2S4/Co9S8 hollow nanospheres and activated carbon achieved a high energy density up to 36.7 Wh kg-1 at 800 W kg-1, suggesting that it could be a promising electroactive material for energy storage devices.

In situ construction of WO3 nanoparticles decorated Bi2MoO6 microspheres for boosting photocatalytic degradation of refractory pollutants.

Visible-light-driven (VLD) heterojunction photocatalysts for refractory contaminant degradation have aroused huge interest because of their outstanding photocatalytic performance. From the aspect of practical application, it is important to develop a highly efficient, durable, eco-friendly and inexpensive VLD photocatalyst. Herein, we report a novel VLD WO3/Bi2MoO6 heterojunction photocatalyst with remarkable photocatalytic activity, which was fabricated via an electrospinning-calcination-solvothermal route. The phase, composition, morphologies, and optical properties of WO3/Bi2MoO6 heterojunctions were comprehensively characterized. The photocatalytic performance of WO3/Bi2MoO6 heterojunctions was assessed by the removal of rhodamine (RhB) and tetracycline hydrochloride (TC) under visible light (VL). WO3/Bi2MoO6 heterojunctions displayed superior photocatalytic activities compared to Bi2MoO6, WO3, or the mechanical mixture of WO3 and Bi2MoO6. In particular, the heterojunction material (0.4WB, theoretical molar ratio of WO3/Bi2MoO6 is 0.4/1.0) exhibited the best degradation efficiency (100%) and mineralization rate (52.3%) in 90 min, both of which exceeded the observed rates for Bi2MoO6 by 5.3 and 6.4 times, respectively. Moreover, 0.4WB showed a good durability in eight runs. The optimized photocatalytic property of WO3/Bi2MoO6 can be attributed to enhanced VL absorption and reduced recombination efficiency of carriers owing to the synergistic effects between Bi2MoO6 and WO3. The necessity of direct contact between WO3/Bi2MoO6 and contaminants was experimentally verified. The study on photocatalytic mechanism demonstrates that superoxide free radicals (O2-) and photo-generated hole (h+) are dominantly responsible for the pollutant degradation, as demonstrated by the trapping experiments and electron spin resonance (ESR) analysis. Therefore, the WO3/Bi2MoO6 heterojunction holds huge potential to be utilized as a durable and highly active photocatalyst for wastewater treatment.

Hierarchical assembly of manganese dioxide nanosheets on one-dimensional titanium nitride nanofibers for high-performance supercapacitors.

MnO2 has attracted considerable attention for use in supercapacitors. Nevertheless, its low electrical conductivity greatly hinders its potential application. Here, we demonstrate the fabrication of a high-performance electrode material via facile coating of hierarchical MnO2 nanosheets onto highly electrically conductive one-dimensional (1D) TiN nanofibers for use in supercapacitors. The TiN nanofibers are prepared through nitridation electrospinning of TiO2 nanofibers via ammonia annealing. The obtained TiN@MnO2 composites exhibit enhanced electrochemical properties, such as high specific capacitance of 386 F/g at a current density of 1 A/g, and long cycle stability of ∼111.7% capacity retention after 4000 cycles at 6 A/g. The unique nanostructure and significant synergistic effect between TiN and MnO2 are responsible for its good electrochemical performance.

Synthesis of hollow NiCo2O4 nanospheres with large specific surface area for asymmetric supercapacitors.

Hollow micro-/nanostructured electrode materials with high active surface area are highly desirable for achieving outstanding electrochemical properties. Herein, we report the successful synthesis of hierarchical hollow NiCo2O4 nanospheres with high surface area as electrode materials for supercapacitors. Electrochemical measurements prove that such electrode materials exhibit excellent electrochemical behavior with a specific capacitance reaching 1229 F/g at 1 A/g, remarkable rate performance (∼83.6% retention from 1 to 25 A/g) and good cycling performance (86.3% after 3000 cycles). Furthermore, the asymmetric supercapacitor is fabricated with hollow NiCo2O4 nanospheres electrode and activated carbon (AC) electrode as the positive and negative, respectively. This device exhibits a maximum energy density of 21.5 W h/kg, excellent cycling performance and coulombic efficiency. The results show that hollow NiCo2O4 nanosphere electrode is a promising electrode material for the future application in high performance supercapacitors.

Hierarchical hollow MnO2 nanofibers with enhanced supercapacitor performance.

One dimensional (1D) hollow nanostructures have been considered as one of the most fascinating materials for supercapacitors. Herein, the hollow MnO2 nanofibers are successfully synthesized through a two-step process, in which the electrospun carbon nanofibers acted as sacrificial template. The resulting hollow nanofibers are composed of ultrathin MnO2 nanosheets, which can offer rich electrochemical active sites for electrochemical reactions. Importantly, the open and free interspaces among these ultrathin MnO2 nanosheets can significantly enhance the utilization of the active material even at high current density. Such unique hollow nanostructure endow the hollow MnO2 nanofibers electrode better electrochemical performance with specific capacitance of 291 F/g at 1 A/g, superior rate capability of ∼73% (from 1 to 10 A/g), and excellent cycling stability of 90.9% retention after 5000 cycles, demonstrating the potential for practical application in energy storage devices.

Improving the cycling stability of lithium-sulfur batteries by hollow dual-shell coating.

Herein, a novel hybrid S@MnO2@C nanosphere, comprising sulfur nanoparticles encapsulated by a MnO2@C hollow dual-shell, is reported. Benefiting from a conductive C outer layer, the S@MnO2@C hybrid nanosphere provided highly efficient pathways for fast electron/ion transfer and sufficient free space for the expansion of the encapsulated sulfur nanoparticles. Moreover, the dual-shell composed of a MnO2 inner layer and a C outer layer coating on S not only improved the efficacious encapsulation of sulfur, but also significantly suppressed the dissolution of polysulfides during cycling. As a result, the S@MnO2@C electrode shows high capacity, high coulombic efficiency and excellent cycling stability. The S@MnO2@C cathode delivered a discharge capacity of 593 mA h g-1 in the fourth cycle and was able to maintain 573 mA h g-1 after 100 charge-discharge cycles at 1.0C, corresponding to a capacity retention of 96.6%.

Chemical Decoration of Perovskites by Nickel Oxide Doping for Efficient and Stable Perovskite Solar Cells.

Crystal engineering of CH3NH3PbI3- xCl x perovskite films through modification by decoration with p-type semiconductor materials was proposed as an efficient method for obtaining good-quality crystalline films. A simple method is demonstrated to improve the quality of perovskite films by adding nickel oxide (NiO x) nanoparticles into the precursor solution. The addition of NiO x brings about high-quality crystals and convenient photo-generated charge transport with reduced defect density owing to efficient control of the preferred nucleation and crystal growth. The sufficient contact between CH3NH3PbI3- xCl x-NiO x and the electron-transport layer can contribute to photo-generated carrier lifetime and transport through the optimized interface. Moreover, it is demonstrated that a strong chemical bonding interaction between MAPbI3- xCl x and NiO x could protect perovskite materials from oxygen and humidity corrosion, showing remarkable stability holding ∼81% of the initial power conversion efficiency (PCE) after 50 days. The device with the best PCE of 19.34% is achieved because of the improved short-circuit current from 22.23 to 23.01 mA cm-2 and fill factor from 68.97 to 75.06%. The results certify that this p-type charge transport material decoration method for the optimization of perovskite films is an efficient way to optimize the performance.

Hierarchical heterostructures of Bi2MoO6 microflowers decorated with Ag2CO3 nanoparticles for efficient visible-light-driven photocatalytic removal of toxic pollutants.

Developing highly active and durable visible-light-driven photocatalysts for the degradation of toxic pollutants is of vital significance. Herein, Ag2CO3 nanoparticles were in situ formed on Bi2MoO6 microflowers to produce Ag2CO3/Bi2MoO6 heterostructures via a facile procedure. The morphologies, phases, chemical compositions, and optical properties of Ag2CO3/Bi2MoO6 were examined by multiple characterization techniques. The Ag2CO3/Bi2MoO6 heterostructures exhibited substantially improved performance in the removal of industrial dyes (rhodamine B (RhB), methyl orange (MO), and methyl blue (MB)), and the antibiotic tetracycline hydrochloride (TC), compared with bare Bi2MoO6 and Ag2CO3 under visible-light irradiation. The enhancement of activity was attributed to the high charge-separation capacity, which results from the matched band alignment of the two components. The cycling experiments showed a good durability of Ag2CO3/Bi2MoO6. Holes were found to be the dominant active species accounting for the pollutant degradation. This compound is a promising candidate for wastewater treatment.

Synthesis of Flower-Like AgI/BiOCOOH p-n Heterojunctions With Enhanced Visible-Light Photocatalytic Performance for the Removal of Toxic Pollutants.

In this study, flower-like AgI/BiOCOOH heterojunctions were constructed through a two-step procedure involving the solvothermal synthesis of BiOCOOH microflowers followed by AgI modification using a precipitation method. These novel photocatalysts were systematically examined by XRD, UV-vis DRS, SEM, TEM, EDS, and PL spectroscopy techniques. The AgI/BiOCOOH heterojunction were studied as a decent photocatalyst for the removal of the industrial dye (rhodamine B, and methyl blue) and antibiotic (tetracycline) under visible light. The AgI/BiOCOOH heterojunctions are much more active than bare BiOCOOH, and AgI, which could be ascribed to the improved separation of charge carriers, resulting from the formation of p-n heterojunction between two constituents. The holes (h+) and superoxide radical (•O 2 - ) were detected as the main active species responsible for the pollutant degradation. The results showed that a highly efficient visible-light-driven photocatalytic system was developed for the decomposition of toxic pollutants.