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In situ imaging of LiO2 dynamics in LOBs with Au/CNT cathode was conducted by ETEM. During discharge, LiO2 formed from Li15Au4 seeds with stability for several minutes. The de-activation of Lifacilitates the nucleation and stabilization of LiO2.

Akin to Li, Na deposits in a dendritic form to cause short circuit in Na metal batteries. However, the growth mechanisms and related mechanical properties of Na dendrites remain largely unknown. He...

Mn-based hexacyanoferrate (Mn-HCF) cathodes for Na-ion batteries usually suffer from poor reversibility and capacity decay resulting from unfavorable phase transitions and structural degradation during cycling. To address this issue, the high-entropy concept is here applied to Mn-HCF materials, significantly improving the sodium storage capabilities of this system via a solid-solution mechanism with minor crystallographic changes upon de-/sodiation. Complementary structural, electrochemical, and computational characterization methods are used to compare the behavior of high-, medium-, and low-entropy multicomponent Mn-HCFs resolving, to our knowledge for the first time, the link between configurational entropy/compositional disorder (entropy-mediated suppression of phase transitions, etc.) and cycling performance/stability in this promising class of next-generation cathode materials.

Lithium metal is considered the ultimate anode material for future rechargeable batteries1,2, but the development of Li metal-based rechargeable batteries has achieved only limited success due to uncontrollable Li dendrite growth3–7. In a broad class of all-solid-state Li batteries, one approach to suppress Li dendrite growth has been the use of mechanically stiff solid electrolytes8,9. However, Li dendrites still grow through them10,11. Resolving this issue requires a fundamental understanding of the growth and associated electro-chemo-mechanical behaviour of Li dendrites. Here, we report in situ growth observation and stress measurement of individual Li whiskers, the primary Li dendrite morphologies12. We combine an atomic force microscope with an environmental transmission electron microscope in a novel experimental set-up. At room temperature, a submicrometre whisker grows under an applied voltage (overpotential) against the atomic force microscope tip, generating a growth stress up to 130 MPa; this value is substantially higher than the stresses previously reported for bulk13 and micrometre-sized Li14. The measured yield strength of Li whiskers under pure mechanical loading reaches as high as 244 MPa. Our results provide quantitative benchmarks for the design of Li dendrite growth suppression strategies in all-solid-state batteries. Lithium whisker growth and mechanical properties can be studied in situ using a combination of two microscopies.

MnO@C/CNTs compounds with adjustable thickness to achieve excellent electromagnetic wave (EMW) absorption performance are successfully fabricated by combining a chemical vapor deposition (CVD) method and carbonization process. The obtained worm hollow MnO@C/CNTs nanostructures have a synergistic effect between the MnO microspheres and the carbon shell layers, and a specific amount of carbon nanotubes (CNTs) can improve the overall conductivity of the composite material, resulting in multipolar polarization, surface polarization and concomitant relaxation. Under the optimized state, the MnO@C/CNTs composites present the best EMW absorption performance, with the reflection loss (RL) value of −60.5 dB and the effective absorption bandwidth (

A facile yet rational strategy is highly desired for the synthesis of high-value-added carbon materials from cheap petroleum asphalt. Here, we develop an in situ texturing strategy for the synthesi...

Lithiation, sodiation, and potassiation usually induce volume expansion to the host structure due to the insertion of alkali metal ions into the host structure. Here we report an unusual volume shrinkage phenomenon during the potassiation of CuO nanowires. The volume shrinkage is caused by an “oxygen pump” and an electrochemically driven Kirkendall effect, in which the O2− ions in the CuO lattice and the K+ migrate asymmetrically under external electric field due to their different mass-to-charge ratio. This is the first direct observation on the “oxygen pump” and electrochemical Kirkendall effect induced volume shrinkage phenomenon, which reveals peculiar ion transport characteristic during electrochemical reactions.

Dielectric composites with high thermal conductivity and mechanical strength have great potential in microelectronic packaging. However, conventional composites with excellent thermal conductivity generally possess high electrical conductivity which raises short-circuit problems and unsatisfactory mechanical properties which limits their applications. In this work, dielectric composites with superior thermal and mechanical performance are obtained by fabricating a new type of fillers with three-dimensional (3D) nanostructure. Specially speaking, carbon nanotubes (CNTs) are grown on the surface of boron nitride nanosheets (BNNS) by chemical vapor deposition (CVD), and then utilized as fillers in epoxy resin (BNNS/CNT/Epoxy). The thermal, mechanical and dielectric properties of as-prepared composites are investigated in details. It is shown that the cross-plane thermal conductivity enhancement of the novel composite is as high as 615% compared with the pure epoxy, higher than that of BNNS/Epoxy (380%). Meanwhile, the BNNS/CNT/Epoxy remains a high electrical resistivity of more than 1 Mohm·cm, which is important to avoid short-circuit in electronics. The tensile strength of the composite increases nearly 4 times with the increase of CVD time. These experimental results indicate that the fabricated BNNS/CNT has great potential for reinforcement of composites with wide applications.

Rational design of heterogeneous non-noble metal catalysts as highly efficient and selective catalysts for hydrogenation of nitroarenes with hydrogen as the reducing agent is currently a great challenge, which has attracted a great deal of attention. Herein, a new strategy for achieving atomic dispersion of Ni atoms on nitrogen-doped porous carbon (Ni–N–C) with a specific surface area of up to 810 m2 g−1 and nickel loading as high as 4.4 wt% is developed, yielding high activity, chemoselectivity, and reusability of catalysts in the hydrogenation of nitroarenes using hydrogen as the reductant with a turnover of number (TON) value of 84 and a turnover of frequency (TOF) value of 8.4 h−1 for the first time. The Ni single atoms anchored on N-doped porous carbon by binding with nitrogen/carbon have been proved to be the active sites. Importantly, the Ni–N3 active species is found to contribute more activity compared with Ni–N2 and Ni–N4. Density functional theory (DFT) calculations also reveal that the Ni–N3 structure exhibits the highest activity according to the lowest adsorption energy and the longest elongation N–O bonds of nitrobenzene, which originated from the induced charge transfer. This work opens a new route for rational design and accurate modulation of nanostructured organic molecular transformation catalysts at the atomic scale.

Carbon dioxide (CO2) as a greenhouse gas causes globe warming. Recent studies have shown that CO2 can be harnessed to make an energy storage device through the operation of metal-CO2 batteries. While the Li-CO2 and Na-CO2 batteries showing high capacity and good cycle life have been demonstrated, the possibility of creating a K-CO2 battery has not been realized. Here we report the creation of a K-CO2 battery by using CO2 as the cathode in an advanced aberration corrected environmental transmission electron microscope, and in-situ observation of the discharge and charge processes of the nanobattery. During discharge, K2CO3 was generated in the cathode, which converted back to metal K during charge, and the K-CO2 nanobattery demonstrates a good cyclability. Moreover, it is evident that CO gas was released during discharge and the carbon cathode was consumed continuously during charge. Our study provides a fundamental understanding of the K-CO2 battery, which may aid the designing of K-CO2 based energy storage devices.

Facile yet rational design of efficient electrocatalyst toward triiodide reduction reaction is a persistent challenge for the practical application of dye-sensitized solar cell (DSSC). Here we propose a protocol for fabricating atomic N-coordinated cobalt sites (Co-Nx-C) within nanomesh graphene frameworks (Co-NMG). The as-synthesized Co-NMG combines the features of atomically dispersed active sites and interconnected mesoporous structure with high porosity, which makes these active sites fully exposed and accessible while facilitating the mass transport of reactants. As a result, the Co-NMG electrocatalysts with substantial active sites and desired porous architectures exhibit high electrocatalytic activity and long-term electrochemical stability. Electrochemical measurements and DFT calculations reveal that the catalytic sites toward the reduction of triiodide mainly derive from the abundant topological defects, nitrogen dopants, and especially the atomic Co-Nx-C moieties. Furthermore, with Co-NMG as counter electrodes (CEs), the DSSCs display a power conversion efficiency of 9.06%, which is higher than that of Pt CEs (7.71%). This work not only provides a promising CE material for DSSC to address the issues associated with Pt catalyst, but also opens up new avenues for developing nanocarbon based catalysts with desired features for other energy-related applications.

A new type of silica nanosphere supported palladium nanoparticles encapsulated with graphene (denoted as Pd/SiO2@RGO) sandwich nanostructure electrocatalyst is prepared via a two-step reduction method for the first time. The characterization of electrocatalyst morphology and composition is discussed by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The TEM and XRD results show that palladium nanoparticles (Pd NPs) with a narrow size distribution are uniformly dispersed between silica sphere and the graphene layer. The ternary hybrid electrocatalyst exhibits high activity (1533 mA mg−1pd), superior operational durability and anti-poisoning ability (If/Ib = 3.9) compared with other controlled Pd catalysts. Moreover, it significantly reduces the peak potential (ca. 40 mv) and onset potential (ca. 80 mv) than commercial Pd/C, accounting for combination of the merits of SiO2 nanosphere support and the excellent electronic conductivity of RGO while overcoming their shortcomings. We provide an efficient way to fabricate a promising non-platinum anode catalyst for alkaline fuel cells.

Herein, we report a facile yet effective fluorescent nanosensor for the direct, selective and sensitive determination of cerebral Cu2+ in the rat brain microdialysate. The fluorescent nanosensor is constructed by utilizing the strong fluorescent graphene quantum dots (GQDs) as the fluorescent signaling output, which were synthesized via chemical oxidation from 3D nanomesh graphene frameworks (NGFs). Initially, the as-prepared GQDs displays a uniform size with lateral size below 5 nm is observed to exhibit photoluminescence properties. The subsequent addition of Cu2+ into the GQDs mixture results in the significant quenching of the fluorescence of GQDs. The quenching degree of Cu2+ towards GQDs is highly sensitive to the concentration of Cu2+ and shows a linear relationship for Cu2+ within the range from 0.1 μM to 1.0 μM with a limit of detection (LOD) of 0.067 μM which substantially enables the GQDs as a nanosensor for Cu2+. Moreover, the as-fabricated nanosenor displays a high specificity for Cu2+ irrespective of the coexistence of other metal ions, amino acids, and biological substance that endogenously existed in the rat brain and has been employed to successfully determination of Cu2+ in rat brain with the basal value of 2.21 ± 0.76 μM (n = 3).

Boron and nitrogen co-doped graphene-like carbon (BNC) with a gram scale was synthesized via a two-step method including a ball-milling process and a calcination process and used as electrode materials for supercapacitors. High surface area and abundant active sites of graphene-like carbon were created by the ball-milling process. Interestingly, the nitrogen atoms are doped in carbon matrix without any other N sources except for air. The textual and chemical properties can be easily tuned by changing the calcination temperature, and at 900 oC the BNC with a high surface area (802.35 m2/g), a high boron content (2.19 at%), a hierarchical pore size distribution and a relatively high graphitic degree was obtained. It shows an excellent performance of high specific capacitance retention about 78.2% at high current density (199 F/g at 100 A/g) of the initial capacitance (254 F/g at 0.25 A/g) and good cycling stability (90% capacitance retention over 1000 cycles at 100 A/g) measured in a three-electrode system. Furthermore, in a two-electrode system, a specific capacitance of 225 F/g at 0.25 A/g and a good cycling stability (93% capacitance retention over 20,000 cycles at 25 A/g) were achieved by using BNC as electrodes. The strategy of synthesis is facile and effective to fabricate multi-doped graphene-like carbon for promising candidates as electrode materials in supercapacitors.

In the past decades, graphene has attracted much attention as the host material of photodetectors (PDs), owing to its fascinating mechanical property, ultrahigh carrier mobility and remarkable optical transparency. However, the intrinsic low light absorption of graphene affects its comprehensive application in PDs. Therefore, graphene-based PDs research has focused on hybrid system and optimized graphene structures to enhance photoabsorption. In order to combine the advantages of both approaches, we successfully prepared crumpled reduced graphene oxide (C-rGO) for PDs by a simple ultrasonic pyrolysis method. Through this rapid, one-step capillary-driven route, C-rGO and C-rGO/(ZnO,PbS) composite films can be easily deposited on arbitrary substrates (PET, glass, Al2O3 ceramic and paper). Interestingly, the unique C-rGO PDs shows superior stability and fast transient photocurrent response (rise/decay time of 189/189 ms). Furthermore, by incorporating ZnO and PbS nanoparticles to enhance light absorption, the crumpled hybrid nanostructure PDs demonstrate about four times increased photocurrents and broad-band (UV–Vis–NIR) photodetection features with R of 0.12 A/W. Such crumpled C-rGO-based PDs hold great potentials for future optoelectronic applications, and the ultrasonic pyrolysis method could open a new way for engineering novel nanostructured thin films with high-performance photodetection.

Molybdenum disulfide (MoS2) has attracted a great deal of attention to its unique properties in recent years. In this work, a scalable and green method was developed for the production of high-quality MoS2 nanosheets using shear-assisted supercritical CO2 exfoliation. Our experiments indicate that high temperature, pressure, and shearing speed are favorable to the exfoliation of MoS2. It is found that over 95% of the exfoliated MoS2 nanosheets are less than 10 layers, among which about 50% are 1–4 layers. Raman spectra and XRD patterns reveal that few-layer MoS2 nanosheets with high planar crystal structure are successfully prepared. Moreover, the produced MoS2 has a better stability in N-methyl-pyrrolidone (NMP) than the bulk MoS2. The concentration of the exfoliated MoS2 in NMP after sedimentation for 7 days is as high as 0.97 mg/ml.

The fabricating of transparent conductive films with low resistance, high transparency, flexibility and air stability is significant in the study of flexible electronics. In this work, Cu nanowire/Graphene/Al doped ZnO (Cu/Gra/AZO) composite transparent conductive films were fabricated on PET substrate at room temperature. It is found that this composite film has a high transmittance of 74% at 550 nm, a low sheet resistance of 9.40 Ω/sq and good air stability. In this sandwich structure electrode, Cu nanowires (NWs) play an important role for ensuring the low resistance of the composite film, and the addition of graphene further reduces the resistance plus protects Cu NWs from oxidation. Moreover, the top layer AZO can protect the graphene layer from external damage and improve its stability.

Promoting the Al-water reaction in a neutral condition without adding any sacrificial agents and generating no poisonous byproduct is always the aim of green production of hydrogen. In this study, we fabricated the reduced graphene oxide wrapped aluminum nanoparticles (Al@rGO) through an ultrasonic atomization process. And a high-efficiency hydrogen production is realized in pure water under the infrared light irradiation. Firstly, the graphene wrapping keeps the activity of aluminum nanoparticles by preventing the formation of dense passivation films on the surface of Al and accelerating the ions migration between Al and water. Secondly, the water temperature is enhanced due to the infrared light absorption of graphene, which contributes to the improved hydrogen generation as well. Moreover, the residual byproduct is nature-friendly and recyclable for toxic ion absorption applications. Our results provide an important technique towards the large scale green production of hydrogen by Al@rGO.

Phosphorus-doped porous graphene nanosheet with a large specific surface area (1627.8 m 2 g −1 ) was prepared via chemical vapour deposition (CVD) with porous Mg 3 (PO 4 ) 2 as phosphorus (P) source and template, then it was applied as the counter electrode (CE) for dye-sensitized solar cell (DSSC). Due to the enhanced intrinsic catalytic activity induced by P doping, along with abundant open edge sites originated from the unique porous nanosheet, DSSCs with P doped porous graphene nanosheets CEs exhibited a high power conversion efficiency of 7.08%, which was comparable to that of DSSCs with Pt CEs.

Using α-manganese dioxide (α-MnO2) nanowires as the air electrode, a K-O2 nanobattery is assembled in an aberration corrected environmental transmission electron microscope. It is found that the α-MnO2 nanowires are reduced into Mn3O4 and MnO during discharge; meanwhile, KO2 is formed on the surface of the α-MnO2 nanowires.

Readily prepared CuO nanowires (CuO NWs) have been found to be effective heterogeneous catalysts for the 1,3-dipolar cycloaddition (CuAAC) reaction without using any additional support and bases. Examination of CuO nanowire catalysts synthesized at various temperatures showed that the use of CuO-600 catalyst was the best choice for the success of the present click reaction. Not only aromatic and heteroaromatic alkynes but also alkylalkynes were catalyzed regioselectively, affording triazoles in excellent yields. Furthermore, we have identified that the reaction proceeded in a heterogeneous manner. It is noteworthy that the CuO-600 catalyst can be easily recovered and reused nine times.

Exploiting cost-effective and efficient counter electrodes (CEs) for the reduction of triiodide (I3−) has been a persistent objective for the development of dye-sensitized solar cells (DSSCs). Here, we propose a strategy for the synthesis of nitrogen and sulfur dual-doped porous carbon (N/S-PC) via a thermal annealing approach by using melamine as N source, and basic magnesium sulfate (BMS) whiskers as S source and templates. Benefiting from the high surface area, unique interconnected structural feature and synergistic effects of N/S dual-doping, the N/S-PC shows excellent electrocatalytic activity toward I3− reduction, which has simultaneously been confirmed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The DSSC devices with N/S-PC CEs exhibit a PCE up to 7.41%, which is higher than that of DSSC devices with single heteroatom (N or S) doped CEs and even Pt CEs (7.14%).

In this work, an in situ transmission electron microscopy (TEM) study of the electrochemically driven sodiation and desodiation of a CuO nanowire (NW) was performed. Upon sodiation, Na ions first reacted with CuO, yielding a mixture of Cu, Cu2O, and Na2O, and then some Cu2O was subsequently reduced into nanocrystal Cu. The final sodiation product was nanocrystalline Cu mixed with Na2O and Cu2O. Upon extraction of Na+, the nanocrystalline Cu first oxidized into Cu2O and finally transformed back to nanocrystalline CuO. The volume of the CuO NW was found to expand markedly during the first sodiation, but the morphology of the NW remained unchanged during the following cycles. The mechanism by which high-performance CuO NW anodes are used for rechargeable Na ion batteries was analyzed by carrying out an in situ TEM technique based on our results, and this study may be beneficial for designing the optimal structure of the CuO anode, improving its cycle performance, and making CuO more feasible for Na ion batteries.

Wetlands are an important part of the global soil organic carbon pool and microorganisms play a pivotal role in carbon exchange between soils and atmosphere. Most wetland carbon studies have focused on boreal freshwater wetlands, especially peatlands. Less attention has been paid on the estuarine wetlands where variation in tide salinity can highly affect microbiology and carbon sequestration ability of the wetland soils. In this study, two representative estuarine wetlands in the Yangtze River estuary were chosen to determine the possible differences in microbial communities and activities between coastal (high salinity) and riparian (low salinity) zones of both wetlands. Over a 4-year period, the mean soil respiration of the coastal zones was significantly lower (P

Estuarine wetlands undergoing rapid succession have high organic carbon accumulation rates due to their high primary productivity. A previous study indicated that organic carbon storage in soil differed among successional stages of the Chongming Dongtan tidal wetland due to differences in soil microbial respiration (SMR) and plant biomass. To investigate the mechanisms underlying the differences in SMR, variability in microbial and physicochemical characteristics of soil from different successional stages was studied. Bacterial community composition varied among the successional stages. Some dominant and site-specific bacteria inhabiting the tidal flat may have influenced SMR and soil carbon storage capability. Uncultured members of the Cytophagales and Pseudomonas genera, which include efficient degraders of complex organic compounds, were found primarily in the high tidal flat where the highest SMR and relatively low soil organic carbon storage were observed. Soil environment factors such as particle size, salinity, and total nitrogen (TN) may have affected microbial community composition, in particular the dominant bacterial species, and hence, SMR. The relatively small particle size, low salinity, and high TN in the high tidal flat provided suitable conditions for chemoorganotrophic bacteria such as Cytophagales and Pseudomonas species, which are specialized in the degradation of organic matter.

Undisturbed natural wetlands are considered carbon sequesters because of their high primary productivity and low soil microbial respiration (SMR). Tidal wetlands in Yangtze River Estuary are typical and impermanent original ecological coastal salt marshes, and their carbon sequestration functions are of great significance to the balance of carbon emissions from Shanghai. Global warming and its associated effects comprise one of the most serious environmental problems humans are currently facing. To analyze changes in the SMR of tidal wetlands in the Yangtze River Estuary in response to global warming and the associated increase in sea level, a simulation study was conducted in the laboratory. The results show that when organic input is limited, increasing temperature can lead to an initial sharp increase in SMR, but that the SMR reverts to its original level with time even becomes lower. Overall, increasing the temperature does not have a significant effect on SMR because organic input is limited under these conditions. Increasing sea level can accelerate SMR and β-glucosidase activity, but this effect is not significant. This may occur because more nutrients are input by the tide, which facilitates SMR by attenuating the disadvantage associated with the anaerobic environment caused by prolonged water logging. However, synergistic effect of increased temperature and sea level lead to an obvious acceleration in SMR and β-glucosidase activity. In tidal soil in which the soil nutrient levels are low, organic matter input is found to be the dominant factor affecting SMR and microbial activity.

To clarify the effects of artifical disturbances on the soil microbial respiration (SMR) of existed tidal wetlands, the SMR of three typical areas in Chongming Dongtan and Jiuduansha of the Yangtze River Estuary, China, were evaluated. The causes of the differences in the SMR were also evaluated by analyzing the microbial activity factors and community structure, as well as the physical–chemical characteristics of the different wetland soils. The results showed that the SMR of the existed wetlands in the area of siltation promotion was significantly higher (P

To clarify the variation in soil microbial respiration (SMR) in Jiuduansha wetland during different succession stages, the SMR of five typical zones was evaluated. The results showed that the SMR during different successional stages of vegetation varied significantly (P