Ecological stoichiometry of nitrogen, phosphorous, and sulfur in China's forests

Much attention has been paid to the stoichiometry of carbon(C), nitrogen(N), and phosphorus(P) because of their significance for plant growth and climate change. However, other nutrients, such as sulfur(S), are often ignored. In this study, we analyzed the stoichiometry of N, P, and S in leaves of 348 plant species in China's forests. The results show higher N content and higher molar ratios of N/P and P/S in Angiospermae than in Gymnospermae. At the family level, Ulmaceae absorbed more N and P from soils than other families, and Cupressaceae absorbed more S than other families. In addition,except for bamboo and other tropical forests, leaf N and P content of China's forests generally increased from low to middle latitudes and then slightly decreased or plateaued at high latitudes. Plant ecotypes, taxonomic groups, environmental conditions, atmospheric S precipitation, and soil-available N and P significantly affected the distribution and stoichiometry of leaf N, P, and S in China's forests.Our study indicates that China's forests are likely limited by P and S deficiencies which may increase in the future.

Phosphorous and Foliar Applied Nitrogen Improved Productivity and Quality of Potato

Growth, yield and quality of potato are greatly affected by its nutritional management. Foliar application of urea reduces nitrogen losses and increases plant nitrogen use efficiency. This study was therefore planned to evaluate the effect of soil applied phosphorus (DAP) and foliar application of nitrogenous fertilizer (urea) on growth, yield and quality of potato. Experiment was comprised of four different treatments of phosphorus (DAP, 46% P) and nitrogen (urea, 46% N) including a control. Treatments were T0 (DAP 160 + Urea 300 kg/acre), T1 (DAP 160 + Urea 5 kg/acre), T2 (DAP 100 + Urea 6 kg/acre) and T3 (DAP 120 + Urea 8 kg/acre). DAP fertilizer was given as basal dressing at the time of sowing. Foliar applications of nitrogenous fertilizer (urea) were given after 30 of sowing with one week interval in five split doses. Results indicated that T3 remained better regarding productivity and quality of potato. The overall fertilizer efficacy regarding yield and quality was: T3 > T2 > T1 > T0. However, Vitamin C was found maximum in T0.

Direct observation of the distribution of impurity in phosphorous/boron co-doped Si nanocrystals

Doping in Si nanocrystals is an interesting topic and directly studying the distribution of dopants in phosphorous/boron co-doping is an important issue facing the scientific community.In this study,atom probe tomography is performed to study the structures and distribution of impurity in phosphorous/boron co-doped Si nanocrystals/SiO_(2) multilayers.Compared with phosphorous singly doped Si nanocrystals,it is interesting to find that the concentration of phosphorous in co-doped samples can be significantly improved.Theoretical simulation suggests that phosphorous-boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy,which also reduces the formation energy of phosphorous in Si nanocrystals.The results indicate that co-doping can promote the entry of phosphorous impurities into the near-surface and inner sites of Si nanocrystals,which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals such as the observed enhancement of conductivity and sub-band light emission.

Visible light induced photodegradation of organic pollutants on nitrogen and fluorine co-doped TiO_2 photocatalyst

The nitrogen and fluorine co doped TiO 2 polycrystalline powder was synthesized by calcinations of the hydrolysis product of tetra butyl titanate with ammonium fluoride. Nitrogen and fluorine co doping causes the absorption edge of TiO 2 to shift to a lower energy region. The photocatalytic activity of co doped TiO 2 with anatase phases was found to be 2 4 times higher than that of the commercial TiO 2 photocatalyst Degussa P25 for phenol decomposition under visible light irradiation. The co doped TiO 2 powders only contain anatase phases even at 1000℃. Apparently, ammonium fluoride added retarded phase transformation of the TiO 2 powders from anatase to rutile. The substitutional fluorine and interstitial nitrogen atoms in co doped TiO 2 polycrystalline powder were responsible for the vis light response and caused the absorption edge of TiO 2 to shift to a lower energy region.

Preparation of nitrogen and sulfur co-doped ultrathin graphitic carbon via annealing bagasse lignin as potential electrocatalyst towards oxygen reduction reaction in alkaline and acid media

Renewable lignin used for synthesizing materials has been proven to be highly potential in specific electrochemistry.Here,we report a simple method to synthesize nitrogen and sulfur co-doped carbon nanosheets by using bagasse lignin,denoted as lignin-derived carbon(LC).By adjusting the ratio of nitrogen source and annealing temperature,we obtained the ultrathin graphitic lignin carbon(LC-4-1000)with abundant wrinkles with high surface area of 1208 m2g_1 and large pore volume of 1.40 cm3g_1.In alkaline medium,LC-4-1000 has more positive half-wave potential and nearly current density compared to commercial Pt/C for oxygen reduction reaction(ORR).More importantly,LC-4-1000 also exhibits comparable activity and superior stability for ORR in acid medium due to its high graphitic N ratio and a direct four electron pathway for ORR.This study develops a cost-effective and highly efficient method to prepare biocarbon catalyst for ORR in fuel cells.

Nitrogen and Sulfur Co-doped Porous Carbon Derived from ZIF-8 as Oxygen Reduction Reaction Catalyst for Microbial Fuel Cells

Nitrogen and sulfur co-doped porous nanocarbon (ZIF-C-N-S) catalyst was successfully synthesized derived from ZIF-8 and thiourea precursors.The electrochemical measurements indicate that the as-obtained ZIF-C-N-S catalyst exhibits higher electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline electrolyte and superior durability-longer than commercial Pt/C catalyst.The enhancment of electrocatalytic activity mainly be come from the open pore structure,large specific surface area as well as the synergistic effect resulted from the co-doping of N and S atoms.In addition,the ZIF-C-N-S catalyst is also used as the air cathode catalyst in the microbial fuel cell (MFC) device.The maximum power density and stable output voltage of ZIF-C-N-S based MFC are 1315 mW/m2 and 0.48 V,respectively,which is better than that of Pt/C based MFC.

Controllable active sites and facile synthesis of cobalt nanoparticle embedded in nitrogen and sulfur co-doped carbon nanotubes as efficient bifunctional electrocatalysts for oxygen reduction and evolution reactions

Development of efficient and promising bifunctional electrocatalysts for oxygen reduction and evolutionreactions is desirable. Herein, cobalt nanoparticles embedded in nitrogen and sulfur co-doped carbonnanotubes(Co@NSCNT) were prepared by a facile pyrolytic treatment. The cobalt nanoparticles and co-doping of nitrogen and sulfur can improve the electron donor-acceptor characteristics of the carbon nan-otubes and provide more active sites for catalytic oxygen reduction and evolution reactions. The preparedCo@NSCNT, annealed at 900℃, showed excellent electrocatalytic performance and better durability thancommercial platinum catalysts. Additionally, Co@NSCNT-900 catalysts exhibited comparable onset poten-tials and Tafel slopes to ruthenium oxide. Overall, Co@NSCNT showed high activity and improved dura-bility for both oxygen evolution and reduction reactions.

Photocatalytic Destruction of Nitrogen Monoxide over La^(3+) and N Co-doped SrTiO_3 Powders under Visible Light Irradiation

Lanthanum and nitrogen co-doped SrTiO_3 was prepared by a mechanochemical reaction using SrTiO_3, urea and La_2O_3 as the raw materials. The samples were characterized by X-ray diffraction, X-ray photoelectron spectrometer, transmission electron microscopy, and nitrogen adsorption-desorption isotherm measurements. Lanthanum doping could increase the doping content of nitrogen in the sample. The sample prepared with 0.2 mol% La_2O_3, 22 mol% urea and 77.8 mol% SrTiO_3 by mechanochemical reaction, which has nearly the same nitrogen and lanthanum doping fractions, exhibited high photocatalytic activities. Under the irradiation of light with wavelength larger than 400, and 290 nm, the photocatalytic activity of nitrogen and lanthanum co-doped SrTiO_3 were 2.6 and 2 times greater than that of pure SrTiO_3.

Enhancing ammonia production rates from electrochemical nitrogen reduction by engineering three-phase boundary with phosphorus-activated Cu catalysts

Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to its low solubility in aqueous electrolytes.Herein,we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N_(2) molecules.The eNRR system is further modified using a gas diffusion electrode(GDE) coated with polytetrafluoroethylene(PTFE) to form an effective three-phase boundary of liquid water-gas N_(2)-solid catalyst to facilitate easy access of N_(2) to the catalytic sites.As a result,the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH_(3) production rate of 7.69 μg h^(-1) cm^(-2) at-0.2 V_(RHE),which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell.This work represents a successful demonstration of dual modification strategies;catalyst modification and N_(2) supplying system engineering,and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.

Promotion of activation ability of N vacancies to N2 molecules on sulfur-doped graphitic carbon nitride with outstanding photocatalytic nitrogen fixation ability

Nitrogen vacancies and sulfur co-doped g-C3N4 with outstanding N2 photofixation ability was synthesized via dielectric barrier discharge plasma treatment. X-ray diffraction, ultraviolet–visible spectroscopy, N2 adsorption, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and temperature-programmed desorption were used to characterize the as-prepared catalyst. The results showed that plasma treatment cannot change the morphology of the as-prepared catalyst but introduces nitrogen vacancies and sulfur into g-C3N4 lattice simultaneously. The as-prepared co-doped g-C3N4 displays an ammonium ion production rate as high as 6.2 mg·L^-1·h^-1·gcat^-1, which is 2.3 and 25.8 times higher than that of individual N-vacancy-doped g-C3N4 and neat g-C3N4, respectively, as well as showing good catalytic stability. Experimental and density functional theory calculation results indicate that, compared with individual N vacancy doping, the introduction of sulfur can promote the activation ability of N vacancies to N2 molecules, leading to promoted N2 photofixation performance.

Enhancement of photoluminescence of Ba_2SiO_4:Eu^(2+) by co-doping of La^(3+) or Y^(3+)

Green light-emitting Ba2SiO4：Eu^2＋ phosphors co-doped with La or Y were synthesized by conventional solid-state reaction technique in reductive atmosphere（a mixture of 5% H2 and 95% N2）.The results showed that the co-doping of La and Y could greatly enhance the fluorescence intensity of Ba2SiO4：Eu2＋ phosphors.The optimum doping concentration expressed by the x value in（Ba0.985-1.5xREx）2SiO4：0.03Eu^2＋（RE=La or Y） was determined to be of 0.05.The excitation and emission peaks of all as-synthesized phosphors were wide bands.The excitation bands ranged from 250 to 400 nm, which matched well with the wavelength of near ultraviolet white light-emitting diodes（LED） chip and could be used as a potential candidate for the fabrication of white LED.The emission bands from 450 to 550 nm were typical 5d-4f transition emission of Eu^2＋ and displayed un-symmetry profiles because of the two substitution sites of Ba^2＋ with Eu^2＋.

Effects of oxygen/nitrogen co-incorporation on regulation of growth and properties of boron-doped diamond films

Regulation with nitrogen and oxygen co-doping on growth and properties of boron doped diamond films is studied by using laughing gas as dopant. As the concentration of laughing gas(N2O/C) increases from 0 to 10%, the growth rate of diamond film decreases gradually, and the nitrogen-vacancy(NV) center luminescence intensity increases first and then weakens. The results show that oxygen in laughing gas has a strong inhibitory effect on formation of NV centers, and the inhibitory effect would be stronger as the concentration of laughing gas increases. As a result, the film growth rate and nitrogen-related compensation donor decrease, beneficial to increase the acceptor concentration(~3.2×10^(19)cm^(-3)) in the film. Moreover, it is found that the optimal regulation with the quality and electrical properties of boron doped diamond films could be realized by adding appropriate laughing gas, especially the hole mobility(~700cm^(2)/V·s), which is beneficial to the realization of high-quality boron doped diamond films and high-level optoelectronic device applications in the future.

Boosting lithium storage performance of Si nanoparticles via thin carbon and nitrogen/phosphorus co-doped two-dimensional carbon sheet dual encapsulation

Silicon(Si)is a promising anode candidate for next-generation lithium-ion batteries(LIBs),but it suffers from poor electronic conductivity and dramatic volume variation during cycling,which poses a critical challenge for stable battery operation.To mitigate these issues simultaneously,we propose a"double carbon synergistic encapsulation"strategy,namely thin carbon shell and nitrogen/phosphorus co-doped two-dimensional(2D)carbon sheet dual encapsulate Si nanoparticles(denoted as 2D NPC/C@Si).This double carbon structure can serve as a conductive medium and buffer matrix to accommodate the volume expansion of Si nanoparticles and enable fast electron/ion transport,which promotes the formation of a stable solid electrolyte interphase film during cycling.Through structural advantages,the resulting 2 D NPC/C@Si electrode demonstrates a high reversible capacity of592 mAh·g^(-1) at 0.2 A·g^(-1) with 90.5%excellent capacity retention after 100 cycles,outstanding rate capability(148 mAh·g^(-1) at 8 A·g^(-1)),and superior long-term cycling stability(326 mAh·g^(-1) at 1 A·g^(-1) for 500 cycles,86%capacity retention).Our findings elucidate the development of high-performance Si@C composite anodes for advanced LTBs.

Convenient room-temperature synthesis of sulfur and nitrogen co-doped NiCo-LDH coupled with CNTs on NiCo foam as battery-type electrode for high performance hybrid supercapacitor

The convenient synthesis of the composite electrode with high supercapacitance performance plays an important role in practical application but is challenging.Herein,the carbon nanotubes(CNTs)coupled with lowcrystalline sulfur and nitrogen co-doped Ni Co-LDH(denoted as SN-Ni Co-LDH)nanosheets array are grown on Ni Co foam(NCF)substrate by two convenient steps of metal induced self-assembly and corrosion engineering,which present the advantages of operating at roomtemperature and low preparation costs.Benefiting from the S–N co-doping and low-crystallinity of Ni Co-LDH,the prepared SN-Ni Co-LDH@CNTs@NCF electrode presents a topping charge capacity of 2470 C·g^(-1)(4.94 C·cm^(-2))at 5 m A·cm^(-2).Furthermore,the fabricated asymmetry supercapacitor(ASC)achieves an extraordinary energy density of 77 Wh·kg^(-1)(0.617 m Wh·cm^(-2))at a power density of 438 W·kg^(-1)(3.5 m W·cm^(-2))and outstanding stability(91%capacity retention after 5000 cycles at20 m A·cm^(-2)).Impressively,the structure evolution of Ni Co-LDH during the charge/discharge processes has been thoroughly elucidated by in-situ Raman spectra.Therefore,this work verifies a powerful strategy and practical value for preparing composite electrodes with high supercapacitance performance,and also provides guidance for the rational design of the smart electrodes.

Enhanced photocatalytic hydrogen production from Co-MOF/CN by nitrogen and sulfur co-doped coal-based carbon quantum dots

A novel composite photocatalyst for photocatalytic decomposition of water for hydrogen evolution was successfully synthesized by in-situ growth of nitrogen and sulfur co-doped coal-based carbon quantum dots(NSCQDs)nanoparticles on the surface of sheet cobalt-based metal-organic framework(Co-MOF)and graphitic carbon nitride(g-C_(3)N_(4),CN).The structure and properties of the obtained catalysts were systematically analyzed.NSCQDs effectively broaden the absorption of Co-MOF and CN in the visible region.The new composite photocatalyst has high hydrogen production activity and the hydrogen production rate reaches 6254μmol/(g·h)at pH=9.At the same time,NSCQDs synergy Co-MOF/CN composites have good stability.After four cycles of hydrogen production,the performance remains relatively stable.The tran sient photocurrent response and Nyquist plot experimental results further demonstrate the improvement of carrier separation efficiency in composite catalysts.The semiconductor type(n-type semico nductor)of the single-phase catalyst was determined by the Mott-Schottky test,and the band structure was analyzed.The conductive and valence bands of CN are-0.99 and 1.72 eV,respectively,and the conduction and valence bands of Co-MOF are-1.85 and 1.33 eV,respectively.Th e mechanism of the photocatalytic reaction can be inferred,that is,Z-type heterojunction is formed between CN an d Co-MOF,and NSCQDs was used as cocatalyst.

改性玉米芯生物炭的制备及其在废水中的应用

生物炭具备独特的多孔结构和丰富的表官能团,为废水处理、土壤改良、农作物增收、环境修复等提供一类有效的技术材料。本文选取玉米芯为实验材料,采用高浓度磷酸浸泡活化制备玉米芯生物炭,用碘值确定生物炭的最佳制备工艺条件,最后通过扫描电镜(SEM)、X射线衍射(XRD)对最佳制备条件的生物炭进行性能表征分析,并将制备的生物炭去处理模拟废水中氨氮,结果表明:污水中投加改性后的生物炭对氨氮的去除具有良好的处理效果。

油茶树体对氮磷钾元素年吸收和积累规律的研究

以5年生油茶为试材,研究了树体对大量矿质元素氮、磷、钾元素的年吸收和积累规律。结果表明:油茶年发育周期中对氮、磷、钾元素的吸收量分别为44.05、5.50、23.31 g.株-1,吸收比例约为8∶1∶4。抽梢期(4月)至果实发育期(7月)是油茶吸收氮、钾元素的活跃时期,该段时期内的积累量超过了年积累量的50.00%,其中的氮、钾元素分别有43.64%和26.97%被根系所利用;植株对磷元素的积累量在4月至10月没有明显的起伏,从果实发育期(7月)至成熟期(10月)这段时间内,植株磷元素的积累量达到2.63 g,其中35.36%保留在根系中。油茶叶片、枝干和根系中氮、磷、钾元素含量高低顺序为氮>钾>磷,成熟果实中为钾>氮>磷;在新梢期(4月),根系中的磷、钾元素向叶片和新梢进行了部分转运,而在果实膨大、成熟期,钾元素从枝干和叶片转运至果实中。

池塘循环水养殖模式的构建及其对氮磷的去除效果

构建了一个由水源地、养殖池塘、生态沟渠（1级净化）、2级净化塘和3级净化塘组成的淡水池塘循环水养殖模式,研究该模式对池塘养殖废水中氮和磷的去除效果。2010年5—10月的运行结果表明,经过3级净化后,养殖废水中氨氮水平能维持在约0.33 mg.L-1,6月仅为0.010 3 mg.L-1,亚硝酸盐氮含量低于0.02 mg.L-1,总氮含量在各月均能达到GB 3838—2002《地表水环境质量标准》中Ⅴ类标准（≤2.0 mg.L-1）,总磷含量均能达到地表水Ⅲ类标准（≤0.2 mg.L-1）,对叶绿素a的去除效果也很明显,去除率为16.10%~91.22%。可见,该模式能够有效地去除养殖废水中过量的氨氮、亚硝酸盐氮、总氮、总磷和叶绿素a。各级净化模块并不能逐级加倍发挥净化效果,这可能是因为在日常管理过程中由于孽生使得水生植物密度过大,从而引起水质变化反复。近2 a来的试验结果显示新建的淡水池塘循环水养殖模式正处于功能完善阶段,尚未成熟。

植物吸收在人工湿地去除氮、磷中的贡献

探讨了植物在人工湿地系统处理污水中的作用,并分析了影响植物生长的主要环境因素,结合实例分析了湿地植物吸收氮磷在不同生长期的变化和其在去除氮磷营养物中的贡献,认为通过秋冬季的植物收割去除的氮磷量比较低,植物可以作为冬季保温材料而不收割,提出通过组合技术来改善人工湿地氮磷去除能力的思路。