Novel Fe2O3 microspheres composed of triangular star-shaped nanorods as an electrode for supercapacitors.

Fe2O3 microspheres with a unique structure were reported for the first time in this article and showed excellent cycling stability as a negative electrode for supercapacitors. A high areal specific capacitance of 1465.26 mF cm-2 was also achieved in sulfur-doped Fe2O3. An asymmetric supercapacitor was assembled demonstrating its potential for practical use.

Nickel hexacyanocobaltate quantum dots embedded in N-doped carbon for aqueous alkaline batteries with ultrahigh durability.

Nickel-cobalt Prussian blue analogues (Ni-Co PBAs) suffer from structural instability in neural and alkaline electrolytes due to the dissolution of metal cations and cyanide anions caused by external H2O attack, resulting in capacity degradation and restricted life span. Herein, in this work, Ni-Co PBA quantum dots embedded in N-doped carbon (CC-Ni-Co PBA) were synthesized via a facile coprecipitation method and in situ polymerization followed by calcination under a nitrogen atmosphere. The obtained electrode provided a high specific capacity of 333.7 C g-1 and still retained 188.8 C g-1 when the current density increased by 40 times. Remarkably, it exhibited outstanding cycling stability with 82% retention of capacity after 10 000 cycles in an aqueous alkaline electrolyte, which benefited from the inner Ni-Co PBA quantum dots that provided a surrounding space and significantly accommodated the volume change during the repeated charge-discharge process, and the outer carbon layer that served as a protective barrier to hinder the Ni-Co PBA from dissolving into the electrolyte, thus realizing the durability of the electrode. Furthermore, an asymmetric alkaline battery device was assembled which achieved a maximum energy density of 33.2 W h kg-1 and a power density of 3.1 kW kg-1. Our work contributed to the development of PBA-based electrode materials with improved cycling stability as battery-type electrodes in aqueous electrolytes.

Characterization of the dissociation kinetics of Cd and Ni in soils based on diffusive gradients in thin films technique.

A new theoretical method was established for the combinatorial calculation of the dissociation rate constant (K-1) of the metal-organic complexes (MLs), the concentration of free ionic soil metals (CM), the labile concentration of soil metal-organic complexes (CML) based on diffusive gradients in thin-films (DGT) technique with a range of diffusive layer thicknesses (0.053-0.173 mm) in soils. The fitting results agreed well with the determined values. The values of K-1, CML and CM were calculated without other morphological analysis software and the fitting results agreed well with the determined values with some advantages such as the use of fewer hypothetical parameters, ease of calculation, the full embodiment of the contribution of MLs to the labile content. According to the results of model fitting, cation exchange capacity and soil organic matter were found to be the key environmental factors for K-1 values of Cd and Ni, respectively. The labile contents of Cd and Ni in soil were closely related with pH, soil organic matter and the total contents of heavy metals.

[Applications of Geostatistical Analyses and Stochastic Models to Identify Sources of Soil Heavy Metals in Wuqing District, Tianjin,China].

A survey on soil samples was conducted to study the heavy metal pollutions and their potential sources in Wuqing District, Tianjin, China. A total of 578 topsoil samples were collected and the concentrations of eight heavy metals, namely, Cd, Pb, Cu, Zn, Cr, Ni, As (metalloid) and Hg were analyzed. A summary of descriptive statistics, principal component analysis, geostatistical analysis and stochastic forest regression models were applied to study the spatial and temporal variation and identify proportional contribution from either natural or anthropogenic sources for the eight heavy metals in topsoils of the study region. The results indicated that the average concentrations of all the heavy metals except for Cr in the topsoils exceeded their corresponding natural-background values. As, Ni and Cr were mainly contributed by natural sources (i.e., soil parent materials). Cu and Zn originated from both the soil parent materials and sewage irrigation. Pb and Cd originated mainly from non-point source pollution and partially from point source. Hg originated from sewage irrigation. It was proved that combination of multi-technologies provides an effective way to delineate multiple heavy metal pollution sources.