Superior electrocatalytic negative electrode with tailored nitrogen functional group for vanadium redox flow battery

Development of electrodes with high electrocatalytic activity and stability is essential for solving problems that still restrict the extensive application of vanadium redox flow batteries(VRFBs).Here,we designed a novel negative electrode with superior electrocatalytic activity by tailoring nitrogen functional groups,such as newly formed nitro and pyridinic-N transformed to pyridonic-N,from the prenitrogen-doped electrode.It was experimentally confirmed that an electrode with pyridonic-N and nitro fuctional groups(tailored nitrogen-doped graphite felt,TNGF) has superior electrocatalytic acivity with enhanced electron and mass transfer.Density functional theory calulations demonstrated the pyridonic-N and nitro functional groups promoted the adsorption,charge transfer,and bond formation with the vanadium species,which is consistent with expermental results.In addition,the V2+/V3+redox reaction mechanism on pyridonic-N and nitro functional groups was estabilised based on density functional theory(DFT) results.When TNGF was applied to a VRFB,it enabled enhanced-electrolyte utilization and energy efficiencies(EE) of 57.9% and 64.6%,respectively,at a current density of 250 mA cm^(-2).These results are 18.6% and 8.9% higher than those of VRFB with electrode containing graphitic-N and pyridinicN groups.Interestingly,TNGF-based VRFB still operated with an EE of 59% at a high current density of300 mA cm^(-2).The TNGF-based VRFB exhibited stable cycling performance without noticeable decay of EE over 450 charge-discharge cycles at a current density of 250 mA cm^(-2).The results of this study suggest that introducing pyridonic-N and nitro groups on the electrode is effective for improving the electrochemical performance of VRFBs.

Synthesis, Crystal Structure of [(MeC_5H_4)_2Ln(μ-OCH_2CH_2NMe_2)]_2 (Ln=Sm, Y, Nd) and Their Catalytic Activity for Ring-Opening Polymerization of ε-Caprolactone

Reaction of (MeC 5H 4) 3Ln with HOCH 2CH 2NMe 2 in tetrahydrofuran(THF) gives the new complexes [(MeC 5H 4) 2Ln(μ OCH 2CH 2NMe 2)] 2 (Ln=Sm, Y, Nd) with nitrogen functionalized μ alkoxide ligand. The complexes were characterized by elemental analysis and IR, and [(MeC 5H 4) 2Sm(μ OCH 2CH 2NMe 2)] 2 was structurally characterized by the X ray diffraction to be a dimer formed by two unsymmetric oxygen bridges. The complex has a tricyclic skeleton with the additional two Sm-N bonds via intramolecular coordination of OCH 2CH 2NMe 2. The coordination number of the central metal Sm is nine. The title complexes show good catalytic activity for ring opening polymerization of ε caprolactone.

Characterization of the genes involved in nitrogen cycling in wastewater treatment plants using DNA microarray and most probable number-PCR

To improve nitrogen removal performance of wastewater treatment plants （WWTPs）, it is essential to understand the behavior of nitrogen cycling communities, which comprise various microorganisms. This study characterized the quantity and diversity of nitrogen cycling genes in various processes of municipal WWTPs by employing two molecular-based methods：most probable number-polymerase chain reaction （MPN-PCR） and DNA microarray. MPN-PCR analysis revealed that gene quantities were not statistically different among processes, suggesting that conventional actwated sludge processes （CAS） are similar to nitrogen removal processes in their ability to retain an adequate population of nitrogen cycling microorganisms. Furthermore, most processes in the WWTPs that were researched shared a pattern：the nitS and the bacterial amoA genes were more abundant than the nirK and archaeal amoA genes, respectivelv. DNA microarray analysis revealed that several kinds of nitrification and denitrification genes were detected in both CAS and anaerobic-oxic processes （AO）, whereas limited genes were detected in nitrogen removal processes. Results of this study suggest that CAS maintains a diverse community of nitrogen cycling microorganisms; moreover, the microbial communities in nitrogen removal processes may be specific.

Nitrogen-rich carbon spheres made by a continuous spraying process for high-performance supercapacitors

Supercapacitors have high power densities, high efficiencies, and long cycling lifetimes; however, to enable their wider use, their energy densities must be significantly improved. The design and synthesis of improved carbon materials with better capacitance, rate performance, and cycling stability has emerged as the main theme of supercapacitor research. Herein, we report a facile synthetic method to prepare nitrogen-rich carbon particles based on a continuous aerosol- spraying process. The method yields particles that have high surface areas, a uniform microporous structure, and are highly N-doped, resulting in a synergism that enables the construction of supercapacitors with high energy and power density for use in both aqueous and commercial organic electrolytes. Furthermore, we have used density functional theory calculations to show that the improved performance is due to the enhanced wettability and ion adsorption interactions at the carbon/electrolyte interface that result from nitrogen doping. These findings provide new insights into the role of heteroatom doping in the capacitance enhancement of carbon materials; in addition, our method offers an efficient route for large-scale production of doped carbon.

Characteristics of microbial community functional structure of a biological coking wastewater treatment system

Nitrogenous heterocyclic compounds are key pollutants in coking wastewater; however, the functional potential of microbial communities for biodegradation of such contaminants during biological treatment is still elusive. Herein, a high throughput functional gene array（Geo Chip 5.0）in combination with Illumina Hi Seq2500 sequencing was used to compare and characterize the microbial community functional structure in a long run（500 days） bench scale bioreactor treating coking wastewater, with a control system treating synthetic wastewater. Despite the inhibitory toxic pollutants, Geo Chip 5.0 detected almost all key functional gene（average61,940 genes） categories in the coking wastewater sludge. With higher abundance, aromatic ring cleavage dioxygenase genes including multi ring1,2 diox; one ring2,3 diox; catechol represented significant functional potential for degradation of aromatic pollutants which was further confirmed by Illumina Hi Seq2500 analysis results. Response ratio analysis revealed that three nitrogenous compound degrading genes-nbz A（nitro-aromatics）, tdn B（aniline）, and scn ABC（thiocyanate） were unique for coking wastewater treatment, which might be strong cause to increase ammonia level during the aerobic process. Additionally, Hi Seq2500 elucidated carbozole and isoquinoline degradation genes in the system. These findings expanded our understanding on functional potential of microbial communities to remove organic nitrogenous pollutants;hence it will be useful in optimization strategies for biological treatment of coking wastewater.