Two-dimensional bimetallic coordination polymers as bifunctional evolved electrocatalysts for enhanced oxygen evolution reaction and urea oxidation reaction

Two-dimensional coordination polymers(CPs) have aroused tremendous interest as electrocatalysts because the catalytic performance could be fine-tuned by their well-designed coordination layers with highly accessible and active metal sites.However,it remains great challenge for CP-based catalysts to be utilized for electrocatalytic oxidation reactions due to their inefficient activities and low catalytic stabilities.Herein,we applied a mixed-metal strategy to fabricate two-dimensional Co_xNi_(1-x)-CPs with dual active sites for electrocatalytic water and urea oxidation.By metal ratio regulation in the twodimensional layer,an optimized Co_(2/3)Ni_(1/3)-CP exhibits a water oxidation performance with an overpotential of 325 mV at a current density of 10 mA cm^(-2) and a Tafel slope of 86 mV dec^(-1) in alkaline solution for oxygen evolution reaction.Importantly,a lower potential than that of commercial RuO_(2) is observed over20 mA cm^(-2).Co_(2/3)Ni_(1/3)-CP also displays a potential of 1.381 V at 10 mA cm^(-2) for urea oxidation reaction and a Tafel slope of 124 mV dec^(-1).This mixed-metal strategy to maximize synergistic effect of different metal centers may ultimately lead to promising electrocatalysts for small molecule oxidation reaction.

All-organic covalent organic frameworks/perylene diimide urea polymer S-scheme photocatalyst for boosted H_(2) generation

Conjugated covalent organic frameworks(COFs)hold great promise in photocatalytic hydrogen evolution owing to their high crystallinity,large surface area,and distinct structure.However,COFs exhibit poor charge separation.Therefore,investigating highly effective COF-based photocatalysts is crucial.For the first time,conjugated COF/perylene diimide urea polymer(PUP)all-organic heterostructure with S-scheme interfacial charge-transfer channels was successfully developed and manufactured via in situ coupling of the two-dimensional triazine-based imine-linked COF(denoted as TATF-COF)with PUP.The optimal photocatalytic hydrogen-evolution rate of 94.5 mmol h^(-1) g^(-1) for TATF-COF/PUP is 3.5 times that of pure TATF-COF and is comparable to or even higher than that of the previously reported COF-based photocatalysts,resulting in an apparent quantum efficiency of up to 19.7%at 420 nm.The improved directional S-scheme charge transfer driven by the tuned built-in electric field and enhanced oxidation and reduction reaction rates of the photogenerated carriers contribute synergistically to the boosted photocatalytic H_(2) evolution.Experiments and theoretical studies reveal plausible H_(2) evolution and spatial S-scheme charge-separation mechanisms under visible-light irradiation.This study provides advanced methods for constructing all-organic S-scheme high-efficiency photocatalysts by the modulation of band structures.

A novel chain-extended urea containing hyperbranched polymer used as toughening modifier for epoxy resin

A new kind of reactive toughening accelerator for epoxy resin, amine-teminated hyperbranched polymer (H2O-NMe2) was synthesized and characterized by FT-IR spectroscopy. Dynamic mechanical analysis (DMA) was used to study the glass transition temperature (Tg), loss factor (tanδ) and activation energy (Ea) by using multiplexing frequency. The results show that the Ea at glassy relaxation process of modified system is about 70-80 kJ/mol higher than that of unmodified system, and the high modulus and good thermal properties are still maintained.

Release Kinetics of Urea from Polymer Coated Urea and Its Relationship with Coating Penetrability

Four kinds of polymer coated urea(PCU)were put in distilled water at 30℃ to determine the variation of coating penetrability and give a precise description of the urea release kinetics. The urea release from PCU could be divided into four stages: lag stage, swell stage, steady stage and decay stage. The release rate coefficient K, a measure of coating penetrability, was linearly increased at swell stage, but almost not variable at steady stage. At decay stage, the relation of X to time t could be described by the equation K= mtn-1where m and n are the coefficients). When n>1, the coating penetrability was gradually increased, and the urea release from PCU was accelerated; when n=1, the coating penetrability was steady, and the urea release from PCU obeyed the first-order kinetics; and when n<1.the coating penetrability was gradually decreased, and the urea release from PCU was delayed, resulting in a significant 'tailing effect'.

Electrochemical Performance of Solid Polymer Electrolyte PEO_(20)-LiTf-Urea_(1.5)

A new solid polymer electrolyte PEO20-LiTf-Urea1.5 was prepared by solution casting technique. The energy of frontier orbitals for the components of the electrolyte was predicted by quantum chemistry calculations, and TG stability and electrochemical features were measured. Urea exhibited a lower HOMO energy than PEO, implying its enhanced stability against electrochemical oxidation. Experimentally addition of urea increases the ionic conductivity, which guarantees conductivity requirement for lithium ion batteries. It also results in significant improved electrochemical stability with good thermal stability. Favorable lithium stripping/plating performance is yielded, and it confirms the good stability of the solid electrolyte interphase for the PEO20-LiTf-Urea1.5 system.

Reducing Nitrogen Loss in Subsurface Tile Drainage Water with Managed Drainage and Polymer-Coated Urea in a River Bottom Soil

Poorly-drained, river bottom soils can be high corn (Zea mays L.) yielding environments, but saturated soil conditions often reduce corn yields. Wabash soils located in river bottoms in Northeast Missouri have not been traditionally tile drained due to high clay content which requires narrow tile drain spacings. Increased land prices in the region have increased interest in tile draining poorly-drained bottom land soils to increase corn yields which could have a deleterious effect on water quality. The objectives of the three-year study were to determine whether use of managed subsurface drainage (MD) in combination with a controlled release N fertilizer could reduce the annual amount of NO3--N loss through tile drainage water compared to free subsurface drainage (FD) with a non-coated urea application. Annual NO3--N loss through tile drainage water with FD ranged from 28.3 to 90.1 kg·N·ha-1. Nitrogen fertilizer source did not affect NO3--N loss through tile drainage water, which was likely due to limited corn uptake over the three-year study due to adverse weather conditions. Averaged over three years, MD reduced tile water drained 52% and NO3--N loss 29% compared to FD. Reduction in NO3--N loss through tile drainage water with MD compared to FD was due to reduced tile flow during the non-cropping period. Annual flow-weighted mean concentration of NO3--N in the tile water was 5.8 mg·N·L-1 with FD and 8.1 mg·N·L-1 with MD. Tile draining river bottom soils at this location for continuous corn production may not pose a health risk over the evaluated duration.

ITSTUDIES ON THE EFFECT OF UREA ON THE COMPATIBILITY OF PMMA/PVC MIXTURES IN DMF BY A DILUTE- SOLUTION VISCOMETRY METHOD

The interaction between poly(methymethacrylate) (PMMA) and poly(vinyl chloride) (PVC) has been studied indilute urea solutions of dimethylformamide (DMF) at 28℃ using a dilute solution viscometry method. The results show thatthe polymer mixtures are compatible in DMF solution in the absence of urea. The influence of urea addition on the degree ofcompatibility of the polymer mixtures has been studied in terms of the compatibility parameters (△b_m and △[η]_m). It wasfound that the compatibility of the polymer mixtures is decreased with increasing urea addition, passing through a minimumat 0.5 M urea.

In Vitro Antimicrobial Activity Study of Some New Arginine-based Biodegradable Poly （Ester Urethane）s and Poly （Ester Urea）s

Bactericidal activity of some arginine based biodegradable polymers-PEURs （poly （ester urethane）s） and PEUs （poly （ester urea）s） with low cytotoxicity was studied in in vitro experiments. Various bacterial strains both Gram-positive and Gram-negative were used to explore the bactericidal activity of the cationic polymers. As the test objects, the following microorganisms were used： Bacillus subtilis, Staphylococcus aureus, Mycobacterium album, Pseudomonas fluorescens, Escherichia coli, Actinomyces griseus and Aspergillus niger. The obtained results showed that the new cationic polymers suppressed the growth of the studied microorganisms and the bactericidal activity of the tested cationic polymers strongly depending on their chemical structure.

自修复聚氨酯-脲的合成与表征综合实验设计

文章结合自修复材料的科研基础,并以自修复聚合物黏结剂在含能复合材料中的需求为导向,设计了一个以国防现代化建设为背景的化学综合实验。该实验以聚氨酯-脲为例,采用甲苯-2,4-二异氰酸酯封端的聚丙二醇和异佛尔酮二胺作为原料合成,通过红外光谱进行结构鉴定,并对产物的自修复性能和黏结能力进行研究。所得聚氨酯-脲具有优异的室温自修复效果,室温下9 h后自修复效率可达87%,同时其与模拟不同含能组分的钢片和有机玻璃片均具有良好的黏结强度。该实验以材料合成—结构—性能—应用为主线,涵盖了较为完整的聚氨酯材料研究的知识体系,在夯实基础理论知识和实验操作技能的基础上,培养研究性学习实践的能力和素养,深化学习强国的价值导向。

A topological polymer network with Cu(Ⅱ)-coordinated reversible imidazole-urea locked unit constructs an ultra-strong self-healing elastomer

It is exceedingly desired, but difficult to construct self-healing materials with both excellent mechanical properties and healing efficiency, which are usually realized by using mutually exclusive methods. Here, we reconcile this contradiction by utilizing copper-bis-(imidazole-2-yl)-methane-urea(Cu-BIMU) locked units based on novel designed dynamic imidazole-urea bonds with coupled multiple noncovalent bonds(coordination bonds, π-π stacking bonds, and hydrogen bonds). The coordination of Cu(II) greatly reduces the electron-cloud density of imidazole, which lowers the free energy barrier of imidazole-urea bonds and promotes their reversible dissociation, as demonstrated by the density functional theory and small-molecule model reaction. The topological design of Cu-BIMU polyurethane(Cu-BIMU-PU), which concentrates multiple crosslinking-in-one locked unit to avoid the formation of excessive crosslinking sites to ensure high chain mobility, facilitates self-healing. Accumulative extensive intermolecular interactions endowed excellent mechanical properties to the resulting Cu-BIMU-PU elastomer with a tensile strength of 65.3 MPa, among the highest ever-reported value. This work provides a novel molecular design principle for fabricating high-performance dynamic polymers.

生物基聚脲酰胺的制备及性能研究

采用一锅两步法熔融缩聚合成了高强高韧的生物基聚脲酰胺(PUA)材料。在无催化剂及无溶剂的条件下,先将尿素与1,10-癸二胺反应合成新型生物基单体二(氨基十亚甲基)脲(DADU),并进一步与1,10-癸二酸(DA10)、1,12-十二碳二酸(DA12)或二聚酸(DmA)熔融缩聚制备了一系列高性能PUA。核磁共振氢谱和傅里叶变换红外光谱证明了PUA的链结构,由体积排阻色谱得出PUA的分子量为12~13 kg/mol。PUA可热压成型,并展现了良好的力学性能,拉伸强度和断裂伸长率分别为25~45 MPa和400%~700%。其中PUA-DA10的拉伸强度达到聚酰胺1010(PA1010)的水平,但断裂伸长率是PA1010的2倍以上,可见其韧性远超于PA1010。PUA-DmA的断裂伸长率不亚于PA-DmA,但是其拉伸强度高于PA-DmA,体现出更高的强度和韧性。本研究证实将脲基引入聚酰胺(PA)得到的PUA可以提高材料的力学性能,该方法十分适合生物基聚酰胺的性能改进和多样化设计与应用。

Coordination Sorption of Urea by Novel Urea Sorbent——Polymer-bound Metal Complexes

<正> Urea can be sorbed by coordination （or complexation）with transitional metalpolyacrylic acid complex and transitional metal-polyacrylamide containing polyethylenepolyamine ligand complexes. The experimental results indicate that the sorbents can sorb about 60mg urea per gram of sorbent at 37℃ and the concentration of urea was 1300.0rag/1 in NaH2PO4and Na2HPO4buffer solution （pH=7.0） and the urea sorption capacity was affected by many factors such as other competive ligands, sorption time, pH and the concentration of urea.

聚合物包膜尿素溶出动力学特征及其与包膜层通透性的关系

通过聚合物包膜尿素(PCU)在30℃纯水中的溶出试验,精确描述了PCU尿素溶出的动力学特征。将PCU尿素溶出过程分成4个阶段:滞后阶段、溶胀阶段、稳定阶段和衰退阶段。同时,基于Fick扩散第一定律,确立了PCU尿素溶出速率与包膜层通透性的关系方程,并根据此方程,推断出PCU尿素溶出过程中包膜层通透性的变化情况。结果表明,在溶胀阶段,溶出速率系数K(包膜层通透性的量度)逐渐变大;在稳定阶段,K为一稳定值;在衰退阶段,K随时间t变化可以用公式K=mt^(n-1)表示(式中m和n均为常数)。当n>1时,包膜层的通透性逐渐增大,肥心尿素溶出加快;当n=1时,包膜层通透性稳定,肥心尿素以一级动力学方式溶出;当n<1时,包膜层通透性逐渐减小,肥心尿素溶出变慢,导致明显的“尾留效应”。

施用保水剂对土壤氮素淋溶及脲酶活性的影响

为了分析保水剂对土壤氮素淋溶效应和土壤脲酶活性影响,通过模拟试验,对施用同量尿素条件下,三种不同类型高分子保水剂(聚丙烯酸钠保水剂、有机-无机复合保水剂、腐植酸型保水剂)对尿素淋溶和土壤脲酶活性进行比较。多次灌水淋溶实验表明,三种保水剂都明显降低了土壤尿素淋失,保肥效果明显。在前三次灌水淋溶中,三种保水剂施用的土壤脲酶活性略高于未施尿素的对照,之后灌水时基本相同,说明保水剂对脲酶活性有一定促进作用,有利于植物更好的吸收氮素。随灌水次数增加,所有处理的土壤脲酶活性都有明显减少,与淋溶液氮素淋出量趋势相同。其中施用聚丙烯酸钠盐保水剂降低氮素流失,提高肥料利用效率效果较优。

用聚合物乳液为包膜剂制备缓释尿素

介绍了采用聚合物乳液作为包膜剂制备包膜缓释尿素,具有工艺简洁和包膜过程绿色的特点,能够根本解决现有包膜过程中毒性有机溶剂的污染和回收问题。实验考察了聚合物乳液包膜剂平板成膜时的渗透系数,表明聚合物乳液是良好的缓释包膜剂。实验采用转鼓流化床工艺制备包膜尿素,测定了包膜尿素在水中的释放特性。通过扫描电镜检测包膜尿素和膜层的形貌特征。结果表明,采用聚合物乳液直接对尿素颗粒包膜时,在颗粒表面形成的高湿性环境容易导致尿素表面溶解,水分蒸发后形成针状尿素结晶,复合在聚合物膜层中,包膜尿素进入水中时,针状尿素快速溶出,造成膜层多孔性渗漏,降低了包膜尿素的缓释性能。在聚合物乳液包膜前,先在尿素颗粒表面包覆一层硫磺阻隔层或石蜡疏水层,能有效抑制尿素在包膜时的溶出过程。

硫膜和树脂膜控释尿素对水稻产量、光合特性及氮肥利用率的影响

本试验以控释期为90d的硫膜(SPCU)和树脂膜(PCU)控释尿素为材料,通过盆栽试验,研究了硫膜和树脂膜控释尿素对水稻产量、光合特性及氮肥利用效率的影响。结果表明,与普通尿素(U)一次基施相比,控释尿素各处理均能显著提高水稻子粒产量、氮肥表观利用率和农学效率,增幅分别达15.1%～51.4%、64.5%～141.1%和5.4～18.2 kg/kg;显著提高水稻生育中后期叶片净光合速率;提高水稻生育中后期的SPAD值。与普通尿素分次施用相比,树脂膜控释尿素及硫膜控释尿素和普通尿素以7∶3比例一次性施入的处理能显著提高水稻子粒产量、氮肥农学效率以及水稻收获后的土壤全氮和碱解氮含量,其增幅分别为7.9%～31.7%、3.3～13.0 kg/kg、2.2%～17.6%和13.2%～22.0%;显著提高叶片中后期的净光合速率,且以树脂膜控释尿素100%一次基施的处理最高。施用树脂膜控释尿素的各处理较普通尿素均能显著提高水稻的氮肥生理效率。树脂膜控释尿素比硫膜控释尿素表现出更好的水稻增产效应和氮肥利用效率,更能有效延缓叶片衰老,实现水稻氮素的高效利用。

以脲和硫脲为主体的高分子固体电解质的研究

研制了一种以脲和硫脲为主体的固体电解质，其室温电导率可达到６．８４×１０－３Ｓ·ｃｍ－１，分析了影响该电解质电导率的因素．初步确定该物质为一种不定型固熔体，导电机理是硫脲转化为硫氰酸铵。

南京郊区番茄地中氮肥的气态氮损失

采用田间试验研究了番茄地施用化学氮肥后的氨挥发、反硝化损失和N2O排放及其影响因素。氨挥发采用通气密闭室法测定，反硝化损失（N2＋N2O）采用乙炔抑制-土柱培养法测定，不加乙炔测定N2O排放。结果表明，番茄生长期间全部处理均未检测到氨挥发，其原因是土表氨分压低于检测灵敏度，较低的氨分压是由于表层土壤的铵态氮浓度和pH都不高所致。在番茄生长期间，对照区即来自有机肥和土壤本身的反硝化损失和N2O℃排放量相当高，反硝化损失总量高达N29．6kghm^-2，N2O排放量为N7．76kghm^-2。施用化学氮肥显著增加了反硝化损失和N2O排放，3个施用化学氮肥处理的反硝化损失变化在N40．8～46．1kghm^-2之间，占施入化肥氮量的5．50％～6．01％；N2O排放量为N13．6～17．6kghm^-2，占施入化肥氮量的2．62％～4．92％；与尿素相比，包衣尿素未能显著减低反硝化损失和N2O排放。施用尿素的处理在每次追肥后，耕层土壤均会出现NO3^--N高峰，继之的反硝化和N2O排放高峰。反硝化速率与土壤含水量呈极显著正相关。总的看来，番茄生长期间没有氨挥发，而硝化反硝化是氮素损失的重要途径之一。

高吸水性树脂包膜尿素的结构特征及养分控/缓释性能

【目的】研究高吸水性树脂包膜尿素的结构特征及养分控/缓释性能。【方法】以不同类型和吸水倍率的高吸水性树脂为包膜材料,以大颗粒尿素和改性矿物包膜尿素为原料肥料,研制出高吸水性树脂单层包膜尿素、高吸水性树脂复式包膜尿素系列产品,利用电子扫描电镜研究了其结构特征,并以水中溶出率法和模拟土柱淋溶法研究其养分释放特性。【结果】高吸水性树脂包膜尿素水中24h氮素溶出率在18.22%～83.87%之间,土壤中4周氮素累积淋出率在40.91%～65.38%之间,较尿素降低5.21%～40.68%。控/缓释性能与高吸水性树脂的类型、吸水倍率及用量有关。聚丙烯酰胺型高吸水性树脂包膜尿素控/缓释效果好于交联聚丙烯酸盐型高吸水性树脂包膜尿素。随着高吸水性树脂用量的增加,高吸水性树脂包膜尿素的水中溶出率和土壤淋出率均明显下降;扫描电镜图显示高吸水性树脂复式包膜尿素的包膜效果明显优于高吸水性树脂单层包膜尿素,其控/缓释效果还与内膜材料有关。高吸水性树脂包膜尿素的内外膜均是由大小不一形状不规则的包膜材料微粒无序紧密堆积,并由胶粘剂填充空隙胶联而成,包膜叠层间和叠层内有微小孔隙,它们是尿素溶出的通道。【结论】高吸水性树脂包膜尿素兼具吸水、保水和养分控/缓释性能,是具有较好开发和应用前景的保水型控/缓释肥料。

二羟甲基脲及其缩聚物的合成与表征

以尿素和甲醛为原料,在碱性水溶液中合成了二羟甲基脲,利用FTIR,1HNMR和元素分析对其结构进行了表征.同时以二羟甲基脲为原料,通过熔融缩聚制备了脲醛缩聚物,通过FTIR,1H NMR,1 3 C NMR和15N NMR对其结构进行了表征.实验结果表明:经二羟甲基脲熔融缩聚制备的长效脲醛缓释化肥,其可利用指数(AI)为98.6%,证明该法是合成长效脲醛肥料的有效途径.