Search

Considering the extensive functional redundancy in microbial communities and great difficulty in elucidating it based on taxonomic structure, studies on the biogeography of soil microbial activity at large spatial scale are as important as microbial community structure. Eighty-four soil samples were collected across a region from south to north China (about 1,000 km) to address the questions if microbial activity displays biogeographic patterns and what are driving forces. These samples represented different soil types, land use and climate. Redundancy analysis and nonmetric multidimensional scaling clearly revealed that soil microbial activities showed distinct differentiation at different sites over a regional spatial scale, which were strongly affected by soil pH, total P, rainfall, temperature, soil type and location. In addition, microbial community structure was greatly influenced by rainfall, location, temperature, soil pH and soil type and was correlated with microbial activity to some extent. Our results suggest that microbial activities display a clear geographic pattern that is greatly altered by geographic distance and reflected by climate, soil pH and total P over large spatial scales. There are common (distance, climate, pH and soil type) but differentiated aspects (TP, SOC and N) in the biogeography of soil microbial community structure and activity.

With the direct carbonization using polyaniline/activated mesocarbon microbead (PANI/ACMB) composites as the precursor and subsequent activation treatment with 16 M HNO3, the activated nitrogen-enriched novel carbons (a-NENCs) can be prepared. Scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption/desorption isotherm at 77 K are utilized to characterize the structure, morphology and physicochemical properties of the a-NENCs. The result shows that the a-NENCs keep the original leechee-like morphology of the PANI/ACMB composites. The supercapacitive performances of the a-NENCs are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge tests, impedance spectroscopy (EIS) and cycle life measurements in 6 M KOH. The results based on galvanostatic charge/discharge tests demonstrate that the maximum specific capacitance of the a-NENCs electrode is 385 F g-1. Meanwhile, the specific capacitance of the button supercapacitor using a-NENCs as electrode active material is as high as 89.5 F g-1 at the charge/discharge current density of 500 mA g-1. These remarkable results demonstrate the exciting commercial potential for high performance, environmentally friendly and low-cost electrical energy-storage devices based on this new material. © 2012 Elsevier B.V. All rights reserved.

The activated nitrogen-enriched novel carbons (a-NENCs) have been prepared by direct carbonization of polyaniline/activated mesocarbon microbead composites and further activated by 16 M HNO3. The electrochemical performances and supercapacitive behaviors of the a-NENCs in 6 M KOH, 1 M H 2SO4, and 0.5 M K2SO4 solutions are evaluated by cyclic voltammetry, galvanostatic charge/discharge, electrochemical impedance spectroscopy, cyclic life, leakage current, and self-discharge measurements. The results demonstrate that the supercapacitors perform definitely supercapacitive behaviors; especially in 6 M KOH electrolyte, the supercapacitor represents much better electrochemical performance with more excellent reversibility, shorter relaxation time of 1.11 s, and nearly ideal polarizability. The maximum specific capacitance of the supercapacitors using a-NENCs as active electrode material is 85.1 F g-1 at a rate of 500 mA g-1 in 6 M KOH. These outcomes indicate that the 6 M KOH aqueous solution is a promising electrolyte for the supercapacitor with a-NENCs as electrode material. © 2013 Springer-Verlag Berlin Heidelberg.

Porous calcium carbide-derived carbon (CCDC) has been prepared by one-step route from CaC2 in a freshly prepared chlorine environment at lower temperature, and following activated by ZnCl2 to get activated CCDC. The performances of the supercapacitors based on activated CCDC as electrode active material in aqueous KOH, K2SO4, KCl and KNO 3 electrolytes are studied by cyclic voltammetry, constant current charged/discharged, cyclic life and electrochemical impedance spectroscopy. It has been found that the supercapacitor using 6 M KOH as electrolyte shows an energy density of 8.3 Wh kg-1 and a power density of 1992 W kg -1 based on the total weight of the electrode active materials with a voltage range 0 V-1 V. Meanwhile, the specific capacitance of the supercapacitor in 6 M KOH electrolyte is 68 F g-1 at the scan rate of 1 mV s-1 in the voltage range of 0 V-1 V, the charge-transfer resistance is extremely low and the relaxation time is the least of all. The supercapacitor also exhibits a good cycling performance and keeps 95% of initial capacity over 5000 cycles. © 2012 Published by Elsevier B.V. All rights reserved.