N,S-Doped Porous Carbon Nanobelts Embedded with MoS2 Nanosheets as a Self-Standing Host for Dendrite-Free Li Metal Anodes.

Metallic Li is one of the most promising anodes for high-energy secondary batteries. However, the enormous volume changes and severe dendrite formation during the Li plating/stripping process hinder the practical application of Li metal anodes (LMAs). We have developed a sulfate-assisted strategy to synthesize a self-standing host composed of N,S-doped porous carbon nanobelts embedded with MoS2 nanosheets (MoS2 @NSPCB) for use in LMAs. In situ measurements and theoretical calculations reveal that the uniformly distributed MoS2 derivatives within the carbon nanobelts serve as stable lithiophilic sites which effectively homogenize Li nucleation and suppress dendrite formation. In addition, the hierarchical porosity and 3D nanobelt networks ensure fast Li-ion diffusion and accommodate the volume change of Li deposits during the plating/stripping process. As a result, a Li-Li symmetric cell using the MoS2 @NSPCB host operates steadily over 1500 h with an ultralow voltage hysteresis (≈24.2 mV) at 3 mA cm-2 /3 mAh cm-2 . When paired with a LiFePO4 cathode, the current collector-free LMA endows the full cell with a high energy density of 460 Wh kg-1 and good cycling performance (with a capacity retention of ≈70% even after 1600 cycles at 10 C).

Determination of hexabromocyclododecanes in sediments from the Haihe River in China by an optimized HPLC-MS-MS method.

Hexabromocyclododecanes (HBCDs), a new type of persistent organic pollutants widely used as brominated flame retardants, have attracted wide attention due to their increasing level and toxicity. A method based on high-performance liquid chromatography mass spectrometry (HPLC-MS-MS) in electrospray ionization mode has been developed by optimization of various parameters, which effectively improved the separation degree and responsive intensity of α-, ß- and γ-HBCD isomers. The concentrations and distribution profiles of three HBCD isomers were investigated in sediments from the Haihe River in China. It was observed that the concentrations of HBCDs varied in the range of 0.4-58.82ng/g, showing a decreasing trend along the flow direction, possibly due to attenuation and biodegradation along the flow direction of the Haihe River. The distribution profile of α-, ß-, γ-HBCD was 7.91%-88.6%, 0-91.47%, and 0.62%-42.83%, respectively. Interestingly, α-HBCD dominated in most sample sites. This was different from the distribution profile in commercial industrial products, which might be attributed to the inter-transformation and different degradation rates of the three HBCD isomers. The potential ecological risk of HBCDs in sediment was characterized under the two-tiered procedure of the European Medicines Evaluation Agency for environmental risk assessment. Although the HBCDs in the selected section of the Haihe River presented "no risk" in the sediment compartment, its risk in sediment cannot be neglected since sediment is one of the important sinks and reservoirs of pollutants.

[Development of Self-assembled Dumbbell-like Fe3O4 Micro/nanomaterial for Application in Thermocatalytic Degradation of Polybrominated Biphenyls].

Polybrominated biphenyls (PBBs) are a group of new persistent organic pollutants, which have high toxicity and long-term bioaccumulation, and cause potential risks to human beings and aquatic ecosystem. Self-assembled dumbbell-like Fe3O4 was synthesized via ethylene-glycol mediated method to degrade PBBs, using BB209 as a model compound. The results showed that the growth process of dumbbell-like Fe3O4 precursor had two stages involving a fast nucleation of amorphous primary particles followed by a slow aggregation and crystallization of primary particles. Dumbbell-like Fe3O4 showed high activity for degradation of BB209 at the reaction time of 30 min with the degradation efficiency of nearly 100% at 300 degrees C. A whole series of nonabromobiphenyl to monobromobiphenyl and biphenyls were detected as the degradation products of BB209 by dumbbell-like Fe3O4, indicating the occurrence of successive hydrodebromination reaction. Furthermore, the amounts of three NoBB isomers followed the order of BB207 > BB208 > BB206, indicating that the reactivity of C--Br of BB209 was in order of meta- > para- > ortho-positions.

Synergetic inhibition of PCDD/F formation from pentachlorophenol by mixtures of urea and calcium oxide.

Chlorophenols are structurally similar to PCDD/Fs and have been considered as highly potential precursors for PCDD/Fs formation. The suppressing effects of PCDD/F formation from pentachlorophenol (PCP) were investigated on various mass ratios of CaO and urea. The total concentration of 2,3,7,8-PCDD/Fs, mostly dominated by OCDD, was determined to be 48.58-10186ng/mg in inhibitor-reaction systems, being much lower than that in blank reaction system (75654ng/mg). Interestingly, compared with pure CaO and urea reaction system, the concentration and TEQ of formed 2,3,7,8-PCDD/Fs in mixed urea/CaO reaction system were lower, especially with 5-20% urea reaction systems being respectively at decrease by 96.5-99.4% and 99.2-99.7%. The suppression efficiency of TEQ in 5-20% urea reaction systems could be always approximately 100% under 250-350°C. These results suggested that mixed inhibitors, especially 5-20% urea inhibitors, have a synergetic inhibition effect for PCDD/Fs formation from PCP. Mixed inhibitor generated several intermediates, involving CO2, H2O, NH3, Ca(OH)2, CaCO3, HNCO, biuret and ammelide. The complex between PCP and Ca, N-doped species, lower chlorinated phenols and benzenediol, and organic acids were also determined. Synergetic inhibition mechanism may be attributed to accelerated facilitation of acid-base reaction and N doping. The decomposition of PCP itself also contributes to prevent PCDD/Fs formation.

Thermal degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) over synthesized Fe-Al composite oxide.

A series of Fe-Al composite oxides were synthesized by the hydrothermal method using different urea dosages and examined towards the degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) at 300 °C. The as-prepared oxides were characterized by field-emission scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy. The morphology and composition of the prepared materials could be regulated by controlling the urea concentration. Interestingly, these properties influenced the nature and amount of the hydrodebromination products generated during the degradation of BDE-47. The degradation of BDE-47 over the composite oxide prepared at a urea dosage of 3 mmol generated BDE-17 as the major isomer product, followed by BDE-28/33, -30, and -32, among the tribromodiphenyl ethers (tri-BDEs). Regarding the dibromodiphenyl ethers (di-BDEs) produced, the amount of the isomers decreased in the order of BDE-8/11 > BDE-7 > BDE-15 > BDE-10. And the BDE-1 among monobromodiphenyl was determined. In contrast, over the composite oxides prepared at urea dosages greater than 3 mmol, BDE-28/33 gradually become the major isomer product instead of BDE-17 among tri-BDEs. The amount of the other di-BDEs isomer such as BDE-15 and -10 approach to be comparable to that BDE-8/11. However, regardless of the urea dosage, BDE-47 converted into BDE-75 via an isomerization reaction. Based on these intermediate products identification, a possible hydrodebromination mechanism of BDE-47 over Fe-Al composite oxide was comprehensively traced.