Anchoring nitrogen-doped Co_(2)P nanoflakes on NiCo_(2)O_(4)nanorod arrays over nickel foam as high-performance 3D electrode for alkaline hydrogen evolution

Effective and robust electrocatalysts are mainly based on innovative materials and unique structures.Herein,we designed a flakelike cobalt phosphide-based catalyst supporting on NiCo_(2)O_(4)nanorods array,which in-situ grew on the nickel foam(NF)current collector,referring as NCo_(2)P/NiCo_(2)O_(4)/NF electrode.By optimizing the microstructure and electronic structure through 3D hierarchy fabrication and nitrogen doping,the catalyst features with abundant electrochemical surface area,favorable surface wettability,excellent electron transport,as well as tailored d band center.Consequently,the as-prepared N-Co_(2)P/NiCo_(2)O_(4)/NF electrode exhibits an impressive HER activity with a low overpotentials of58 mV at 10 mA cm^(-2),a Tafel slop of 75 mV dec^(-1),as well as superior durability in alkaline medium.This work may provide a new pathway to effectively improve the hydrogen evolution performance of transition metal phosphides and to develop promising electrodes for practical electrocatalysis.

Maize straw application as an interlayer improves organic carbon and total nitrogen concentrations in the soil profile: A four-year experiment in a saline soil

Soil salinization is a critical environmental issue restricting agricultural production.Deep return of straw to the soil as an interlayer (at 40 cm depth) has been a popular practice to alleviate salt stress.However,the legacy effects of straw added as an interlayer at different rates on soil organic carbon (SOC) and total nitrogen (TN) in saline soils still remain inconclusive.Therefore,a four-year (2015–2018) field experiment was conducted with four levels (i.e.,0,6,12and 18 Mg ha~(–1)) of straw returned as an interlayer.Compared with no straw interlayer (CK),straw addition increased SOC concentration by 14–32 and 11–57%in the 20–40 and 40–60 cm soil layers,respectively.The increases in soil TN concentration (8–22 and 6–34%in the 20–40 and 40–60 cm soil layers,respectively) were lower than that for SOC concentration,which led to increased soil C:N ratio in the 20–60 cm soil depth.Increases in SOC and TN concentrations in the 20–60 cm soil layer with straw addition led to a decrease in stratification ratios (0–20 cm:20–60 cm),which promoted uniform distributions of SOC and TN in the soil profile.Increases in SOC and TN concentrations were associated with soil salinity and moisture regulation and improved sunflower yield.Generally,compared with other treatments,the application of 12 Mg ha~(–1) straw had higher SOC,TN and C:N ratio,and lower soil stratification ratio in the2015–2017 period.The results highlighted that legacy effects of straw application as an interlayer were maintained for at least four years,and demonstrated that deep soil straw application had a great potential for improving subsoil fertility in salt-affected soils.

Multiscale confinement nitridation in molybdenum carbide for efficient hydrogen production

The molybdenum carbide(Mo_(2)C)has been regarded as one of the most cost-efficient and stable electrocatalyst for the hydrogen evolution reaction(HER)by the virtue of its Pt-like electronic structures.However,the inherent limitation of high density of empty valence band significantly reduces its catalytic reactivity by reason of strong hydrogen desorption resistance.Herein,we propose a multiscale confinement synthesis method to design the nitrogen-rich Mo_(2)C for modulating the band structure via decomposing the pre-coordination bonded polymer in a pressure-tight tube sealing system.Pre-bonded c/N-Mo in the coordination precursor constructs a micro-confinement space,enabling the homogeneous nitrogenization in-situ happened during the formation of Mo_(2)C.Simultaneously,the evolved gases from the precursor decomposition in tube sealing system establish a macro-confinement environment,preventing the lattice N escape and further endowing a continuous nitridation.Combining the multiscale confinement effects,the nitrogen-rich Mo2C displays as high as 25%N-Mo concentration in carbide lattice,leading to a satisfactory band structure.Accordingly,the constructed nitrogen-rich Mo_(2)C reveals an adorable catalytic activity for HER in both alkaline and acid solution.It is anticipated that the multiscale confinement synthesis strategy presents guideline for the rational design of electrocatalysts and beyond.

Characteristics of Soil Organic Carbon, Total Nitrogen, and C/N Ratio in Chinese Apple Orchards

Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.

Nitrogen doped FeS_(2) nanoparticles for efficient and stable hydrogen evolution reaction

Performance breakthrough of electrocatalysts highly relies on the regulation of internal structures and electronic states.In present work,for the first time,we successfully synthesized nitrogen doped FeS_(2) nanoparticles(N-FeS_(2))as the electrocatalysts for hydrogen evolution reaction(HER).The band structure and electronic state of FeS_(2) are modulated by a nitrogen doping strategy,as confirmed by X-ray photoelectron spectroscopy(XPS),X-ray absorption spectroscopy(XAS)and density functional theory(DFT)calculations.Owing to the band structure and electronic state regulation as well as the weakening of H-S interaction,the designed N-FeS_(2) electrocatalyst exhibits superior catalytic performance with a low overpotential(~126 mV at 10 mA cm^(-2))and excellent activity stability under alkaline conditions,which is substantially improved as compared with that of the pure FeS_(2) counterpart.Our work demonstrates that the modulation of electron state and band structure of an electrocatalyst,which can provide a valuable guidance for designing excellent catalysts for hydrogen evolution reaction and beyond.

Nitrogen Dioxide-Induced Responses in Brassica campestris Seedlings: The Role of Hydrogen Peroxide in the Modulation of Antioxidative Level and Induced Resistance

This article investigates the responses of Brassica campestris seedlings to an acute level of nitrogen dioxide （NO2） exposure in a plant growth chamber, and examines whether pretreating plants with hydrogen peroxide （H2O2） will alleviate NO2-caused injury. Twenty-eight-day-old B. campestris plants sprayed with 10 mmol L^-1 H2O2 aqueous solution （corresponding to approximate 1.0 mg H2O2 per single plant） were exposed to different concentrations of NO2 （0.25, 0.5, 1.0, and 2.0 μL L^-1, respectively） for 24 h under controlled environment. To measure the plant biomass, the plants were fumigated with the same NO2 concentrations as mentioned above for 7 h per day （8.00-15.00） for 7 days. As a control, charcoal filtered air alone was applied. Data were collected on plant biomass, total chlorophyll, photosynthetic rate, stomatal conductance, nitrate and nitrate reductase （NR）, antioxidative enzymes, ascorbate （ASA）, and malondialdehyde （MDA）, immediately after exposure. The results showed that exposure to a moderate dose of NO2 （e.g., 0.25 μL L^-1） had a favorable effect on plants, and the dry weight of the above-ground part increased, whereas the exposure to high NO2 concentrations （e.g., 0.5 μL L^-1 or higher） caused a reduction in the plant biomass and the total chlorophyll, when compared with the control. In addition, at 0.5 μL L^-1 or higher NO2 concentrations, prominent increases in the MDA level and superoxide dismutase （SOD） and NR activities were observed. Exposure to 1 μL L^-1 and higher NO2 resulted in necroses appearing on older leaves, and an increase in catalase （CAT） activity, decrease in ASA content, increased accumulation of NO3^-, and reduction in photosynthesis, when compared with the controls. No changes were detected in stomatal conductance under NO2 fumigation. The pretreatment with 10 mmol L^-1 H2O2 alleviated significantly NO2- caused biomass decrease and photosynthetic inhibition when compared with H2O2-untreated plants. Under NO2 fumigation, further induction in SOD and CAT activities occurred in H2O2 treated plants when compared with H2O2- untreated plants. The effect of NO2 on the ASA and MDA contents was also absent in H2O2-treated plants. However, the H2O2 treatment did not alter the nitrate content and NR activity in plants under NO2 fumigation. The H2O2 treatment caused a lower rate of stomatal conductance. Taken together, these data suggest that fumigation with an acute level of NO2 causes oxidative damage to B. campestris seedlings. The H2O2 pretreatment markedly protects plants against NO2 stress and this may be associated with inducible antioxidative level. NO2 fumigation contributes, at least in part, to the enhanced levels of nitrate in B. campestris leaves.

Influence of the concentration ratio of nitrogen to phosphorus on the growth and interspecies competition of two red tide algae

The growth and interspecies competition of two red tide algal species Thalassiosira pseudonana Hasle et Heimdal and Gymnodinium sp. were studied under different concentration ratios of nitrogen to phosphorus, and the algal hatch culture experiments were conducted. The physiological and biochemical indexes were measured periodically, including the maximum comparing growth rate, relative growth rate, average double time and chlorophyll a concentration. The results showed that when the concentration ratio of nitrogen to phosphorus was 16： 1, the maximum comparing growth rate, relative growth rate and chlorophyll a concentration of Thalassiosira pseudonana all reached the highest,and average double time was the shortest. This implied that the optimal concentration ratio of nitrogen to phosphorus of Thalassiosira pseudonana is 16： 1. When the concentration ratio of nitrogen to phosphorus was 6：1, the maximum comparing growth rate, relative growth rate and the chlorophyll a concentration of Gymnodinium sp. reached the highest, and average double time was the shortest, so the optimal concentration ratio of nitrogen to phosphorus of Gymnodinium sp. is 6： 1. From the growth curves as indicated both in the cell density and the chlorophyll a concentration, it is suggested that the influence of concentration ratio of nitrogen to phosphorus on the chlorophyll a concentration and the cell density are almost the same. Different concentration ratios of nitrogen to phosphorus had weak influence on community succession and the competition between the two algae. Gymnodinium sp. may use the phosphorus in vivo for growth, so it is important to pay attention to the concealment of phosphorus, in order to avoid the outbreak of red tide. On the basis of the importance of nitrogen and phosphorus and the ratio of their concentration, the possible outbreak mechanism of red tide of the two algae was also discussed.

Effect of nitrogen to phosphorus ratios on cell proliferation in marine micro algae

The ratio of nitrogen/phosphorus (N/P) is known to affect cell proliferation of some marine micro algae. We evaluated the effect of N/P ratios on the proliferation and succession of phytoplankton using five marine micro algae species. We used two sources of nitrogen, NH4Cl (N1) and urea (N2), and a single source of phosphorous, NaH2PO4(P). The optimal N/P ratio that differed among the five species was affected by the source of nitrogen, being as follows (N1/P, N2/P in order): Thalassiosira sp. (30/1, 20/1), Heterosigma akashiwo (30/1, 30/1), Chroomonas salina (20/1, 30/1), Chaetoceros gracilis (40/1, 60/1), and Alexandrium sp. (10/1, 30/1). Thus, the source of nitrogen must be considered when analyzing the N/P ratio. Our results provide insight for predicting phytoplankton succession in coastal waters and may be used to forecast the potential risk of harmful algal blooms.

Effects of Different Row Ratios of Male and Female Parents and Application Amount of Nitrogen Fertilizer on Hybrid Wheat Seed Production and Its Component Factors

In order to screen suitable high hybrid wheat seed production technology,the split-plot experiment design was adopted and study was carried out about the effects of the different row ratios of male and female parents and application amount of nitrogen fertilizer on hybrid wheat seed production and its component factors. The results showed that the seed production increased with the increase in the number of female parent row. When the row ratio of male and female parents was 2 ∶ 6,the seed production was 3 683. 8 kg/ha; when the application amount of nitrogen fertilization was 50 kg/ha,the seed production was 3 649. 4 kg/ha; the interaction between the row ratio of male and female parents and the application amount of nitrogen fertilizer indicated that when the row ratio of male and female parents was 2∶ 6 and the application amount of nitrogen fertilizer was 300 kg/ha,the seed production reached the highest( 4160. 6 kg/ha). The row ratio of male and female parents and application amount of nitrogen fertilizer had significant effect on the component factors of seed production,including the number of grains per spike,spike weight and setting percentage. When the row ratio of male and female parents was 2∶ 5,the number of grains per spike,spike weight and setting percentage were the highest at 26. 7 grains,1. 12 g,and 62. 6% respectively; when application amount of nitrogen fertilizer was 450 kg/ha,the number of grains per spike,spike weight and setting percentage were the highest at 26. 0 grains,1. 08 g,and59. 2% respectively; the interaction of row ratio of male and female parents and application amount of nitrogen fertilizer had significant effect on the number of grains per spike,spike weight and setting percentage; when the row ratio of male and female parents was 2∶ 5 and the application amount of nitrogen fertilizer was 300 kg/ha,the number of grains per spike,spike weight and setting percentage were the highest at 29. 6grains,1. 24 g,and 71. 6% respectively. The number of grains per spike is the largest component factor for seed production. Increasing the number of grains per spike can increase the seed production. According to the effects of row ratio of male and female parents and application amount of nitrogen fertilizer on the component factors of seed production,the optimal condition was 2∶ 5-2∶ 6 for row ratio of male and female parents and 300-450 kg/ha for application amount of nitrogen fertilizer.

Effects of ambient DIN:DIP ratio on the nitrogen uptake of harmful dinoflagellate Prorocentrum minimum and Prorocentrum donghaiense in turbidistat

The effects of varying nitrogen (N): phosphorus (P) ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO34? in various concentrations to obtain a wide range of N:P ratios. Experiments to determine rates of N uptake and assimilation of different N sources (NO3?, NH4+, urea and glycine by P. minimum and NO3?, NH4+ by P. donghaiense) were conducted using 15N tracer techniques at each N:P ratio. The growth rates suggested nutrient limitation at both high and low N:P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both light- dependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium (low N:P ratio), both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N:P ratios suggested P limitation of N uptake and assimilation. NO3? and NH4+ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3?. Highest average daily growth rates were recorded near an N:P ratio of 12 for both species. The N uptake rates of cultures at N:P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N:P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.

Nitrogen Doped Graphene as Potential Material for Hydrogen Storage

The nitrogen doped graphene was synthesized by hydrothermal route utilizing 2-Chloroethylamine hydrochloride as nitrogen precursor in the presence of graphene oxide (GO). Nitrogen-doped graphene material is developed for its application in hydrogen storage at room temperature. Nitrogen doped graphene layered material shows ~1.5 wt% hydrogen storage capacity achieved at room temperature and 90 bar pressure.

Characterization of the Growth,Chlorophyll Content and Lipid Accumulation in a Marine Microalgae Dunaliella tertiolecta under Different Nitrogen to Phosphorus Ratios

Microalgal lipids are regarded as main future feedstock of biofuels for its higher efficiency of accumulation and sustainable production.In order to investigate the effect of various nitrogen to phosphorus ratios on cells growth,chlorophyll content and accumulation of lipids in Dunaliella tertiolecta,experiments were carried out in modified microalgal medium with inorganic nitrogen(nitrate-nitrogen) or organic nitrogen(urea-nitrogen) as the sole nitrogen source at initial N:P ratios ranging from 1:1 to 32:1.The favorable N:P of 16:1 in the nitrate-N or urea-N medium yielded the maximum cell density and specific growth rate.Decrease in chlorophyll content were observed at the N:P of 4:1 in both nitrate-N and urea-N cultures.It was also observed that the maximum lipids concentration was obtained at the N:P of 4:1 in both nitrate and urea nutrient medium.The lipid productivity and lipid content of cultures in the urea-N medium at the N:P of 4:1were markedly higher than those from cultures with other N:P ratios(p < 0.05).The results of this work illustrate the possibility that higher ratios of nitrogen to phosphorus have enhancing effect on cells growth of D.tertiolecta.Conversely,higher lipid accumulation is associated with a decrease in chlorophyll content under lower ratios of nitrogen to phosphorus.The results confirm the hypothesis of this study that a larger metabolic flux has been channeled to lipid accumulation in D.tertiolecta cells when the ratios of nitrogen to phosphorus drop below a critical level.

Effects of soil nitrate:ammonium ratio on plant carbon:nitrogen ratio and growth rate of Artemisia sphaerocephala seedlings

Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.

Effects of Potassium and Manganese Promoters on Nitrogen-Doped Carbon Nanotube-Supported Iron Catalysts for CO_2 Hydrogenation

氮掺杂碳纳米管(NCNTs)作为载体负载铁(Fe)纳米颗粒,可应用于CO_2多相催化加氢反应(633 K和25 bar)。当将钾(K)和锰(Mn)作为助催化剂时,Fe/NCNT展现出优异的CO_2加氢性能,在体积空速(GHSV)为3.1 L·g^(–1)·h^(–1)时转化率可达34.9%。当使用K作为助催化剂时,反应对烯烃和短链烷烃具有高的选择性。当K和Mn同时作为助催化剂时,其催化活性能够稳定地维持60 h。助催化剂Mn的结构效应通过X射线衍射、氢气程序升温还原以及近边X射线吸收精细结构进行表征。助催化剂Mn不仅能够稳定中间态FeO,且能降低程序升温还原的起始温度。通过探针反应NH3的催化分解来表征助催化剂效应。当K和Mn作为助催化剂时,Fe/NCNT具有最好的催化活性。在还原条件下,当K作为助催化剂时,Fe/NCNT具有最优异的热稳定性。

Facile synthesis of molybdenum carbide nanoparticles in situ decorated on nitrogen-doped porous carbons for hydrogen evolution reaction

Molybdenum-based electrocatalysts are promising candidates of platinum (Pt)-based materials in electrocatalyzing hydrogen evolution reaction (HER), due to their cost-efficient and resembled electronic properties. Reported herein is the preparation of molybdenum carbide nanoparticles uniformly decorated on nitrogen-modified carbons (Mo2C/NC) through the carbonization of Mo-based polymers under hydrogen atmosphere by using poly(p-phenylenediamine) and ammonium heptamolybdate polymer analogue as precursors. And the molybdenum nitride nanoparticles loaded on porous N-doped carbons (Mo2N/NC) are also fabricated by calcination the polymer precursors in nitrogen gas. The Mo2C/NC shows more excellent electrocatalytic activity than Mo2N/NC in 0.5 M H2SO4, together with robust long-term durability. The well-crystalline nanoparticles and the increased electron conductivity are the main characters responded for the high catalytic efficiency of the fabricated electrocatalysts. This easily fabrication procedure may provide a facile route to prepare non-noble metal carbide/nitride catalysts featuring wellengineered structural and textural peculiarities for realistic energy conversion system.

Influences of stoichiometric ratio B/A on structures and electrochemical behaviors of La_(0.75)Mg_(0.25)Ni_(3.5)M_x (M=Ni,Co;x=0-0.6) hydrogen storage alloys

In order to investigate the influences of the stoichiometric ratio of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structures and electrochemical performances of the AB3.5-4.1-type electrode alloys, the La-Mg-Ni-Co system La0.75Mg0.25Ni3.5Mx (M=Ni, Co; x= 0, 0.2, 0.4, 0.6) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The results show that the structures and electrochemical performances of the alloys are closely relevant to the B/A ratio. All the alloys exhibit a multiphase structure, including two major phases, (La, Mg)2Ni7 and LaNi5, and a residual phase LaNi2, and with rising ratio B/A, the (La,Mg)2Ni7 phase decreases and the LaNi5 phase increases significantly. When ratio B/A=3.7, the alloys obtain the maximum discharge capacities. The high rate discharge(HRD) capability of the alloy (M=Ni) monotonously rises with growing B/A ratio, but that of the alloy (M=Co) first mounts up then declines. The cycle stability of the alloy (M=Co) monotonously increases with rising B/A ratio, but it first decreases slightly then increases for the alloy (M=Ni). The discharge potential of the alloy (M=Ni) declines with increasing B/A ratio (x>0.2), but for the alloy (M=Co), the result is contrary. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed ratio B/A=3.7, the Co substitution enhances the discharge capacity from 365.7 to 401.8 mA·h/g, the capacity retention ratio (S100) after 100 charging-discharging cycles from 50.32% to 53.26% and the HRD from 88.65% to 90.69%.

Seasonal Variability of Phytoplankton Community Structure in Relation to Different Nitrogen-Phosphorus Ratios in the Southern Coastal Waters of Zhejiang, China

With the rapid development of economy and increase of population in the drainage areas,the nutrient loading has increased dramatically in the Changjiang estuary and adjacent coastal waters.To properly assess the impact of nutrient enrichment on phytoplankton community,seasonal microcosm experiments were conducted during August 2010 July 2011 in the coastal waters of Zhejiang Province.The results of the present study indicated that the chl a concentration,cell abundance,diversity indices,species composition and community succession of the phytoplankton varied significantly with different N/P ratios and seasons.Higher growth was observed in the 64:1(spring),32:1(summer),16:1(autumn)and 128:1,256:1(winter)treatments,respectively.The values of Shannon-Wiener index(H′)and Pielou evenness index(J)were lower in the 8:1 and 16:1 treatments in autumn test,while H'value was higher in the 128:1 and 8:1 treatments in winter test.A definite community succession order from diatoms to dinoflagellates was observed in the autumn and winter tests,while the diatoms dominated the community throughout the culture in the spring and summer tests.

EFFECTS OF STOICHIOMETRIC RATIO ON STRUCTURE AND ELECTRODE PERFORMANCE OF HYDROGEN STORAGE ALLOYS

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Evaluation on nitrogen isotopes analysis in high-C/N-ratio plants using elemental analyzer/isotope ratio mass spectrometry

Elemental analyzer/isotope ratio mass spectrometry(EA/TRMS) has been widely applied to analyze the^(15)N/^(14)N isotope composition(δ^(15)N) of plants and soils,but the δ^(15)N results may be inaccurate due to incomplete combustion of the high-C/N-ratio plant samples by EA.Therefore,it is necessary to develop a method to solve the problem of imperfect combustion.In this study,we used two methods:1) adding copper oxide powder to the samples,and 2) increasing the O_2 flow(from 100 mL min^(-1) to 200 mL min^(-1)) for the auto sampler inlet purge line of the EA.The δ^(15)N values of the plant samples became more positive and tended to be stable after complete combustion.Also,the required blank samples for each plant sample decreased with increasing amount of the added CuO powder.However,at 200 mL min^(-1) of the oxygen flow in the EA,complete combustion could not be achieved without adding copper oxide,but this was done with decreased amount of CuO powder.Therefore,mixing cupric oxide into the high-C/N-ratio samples was an efficient,simple and convenient way to solve the problem of imperfect combustion in the EA.

Purified oxygenand nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.