A core-shell copper oxides-cobalt oxides heterostructure nanowire arrays for nitrate reduction to ammonia with high yield rate

Electrochemical nitrate reduction to ammonia(NRA) can realize the green synthesis of ammonia(NH3) at ambient conditions, and also remove nitrate contamination in water. However, the current catalysts for NRA still face relatively low NH3yield rate and poor stability. We present here a core-shell heterostructure comprising cobalt oxide anchored on copper oxide nanowire arrays(CuO NWAs@Co_(3)O_(4)) for efficient NRA. The CuO NWAs@Co_(3)O_(4)demonstrates significantly enhanced NRA performance in alkaline media in comparison with plain CuO NWAs and Co_(3)O_(4)flocs. Especially, at-0.23 V vs. RHE, NH_(3) yield rate of the CuO NWAs@Co_(3)O_(4)reaches 1.915 mmol h^(-1)cm^(-2),much higher than those of CuO NWAs(1.472 mmol h^(-1)cm^(-2)), Co_(3)O_(4)flocs(1.222 mmol h^(-1)cm^(-2)) and recent reported Cu-based catalysts.It is proposed that the synergetic effects of the heterostructure combing atom hydrogen adsorption and nitrate reduction lead to the enhanced NRA performance.

Identification of Dynamic Active Sites Among Cu Species Derived from MOFs@CuPc for Electrocatalytic Nitrate Reduction Reaction to Ammonia

Direct electrochemical nitrate reduction reaction(NITRR)is a promising strategy to alleviate the unbalanced nitrogen cycle while achieving the electrosynthesis of ammonia.However,the restructuration of the high-activity Cu-based electrocatalysts in the NITRR process has hindered the identification of dynamical active sites and in-depth investigation of the catalytic mechanism.Herein,Cu species(single-atom,clusters,and nanoparticles)with tunable loading supported on N-doped TiO_(2)/C are successfully manufactured with MOFs@CuPc precursors via the pre-anchor and post-pyrolysis strategy.Restructuration behavior among Cu species is co-dependent on the Cu loading and reaction potential,as evidenced by the advanced operando X-ray absorption spectroscopy,and there exists an incompletely reversible transformation of the restructured structure to the initial state.Notably,restructured CuN_(4)&Cu_(4) deliver the high NH_(3) yield of 88.2 mmol h^(−1)g_(cata)^(−1) and FE(~94.3%)at−0.75 V,resulting from the optimal adsorption of NO_(3)^(−) as well as the rapid conversion of^(*)NH_(2)OH to^(*)NH_(2) intermediates originated from the modulation of charge distribution and d-band center for Cu site.This work not only uncovers CuN_(4)&Cu_(4) have the promising NITRR but also identifies the dynamic Cu species active sites that play a critical role in the efficient electrocatalytic reduction in nitrate to ammonia.

A novel one-step method to synthesize copper nitrate hydroxide nanorings

With the purpose of searching for a convenient process to synthesize nanoparticles with special structure,a simple solid-state reaction in the presence of nonionic surfactant OP-10 at room temperature was adopted to prepare copper nitrate hydroxide(Cu_(2)(OH)_(3)NO_(3))nanorings with an average internal diameter of 250 nm and average wall thickness of 100 nm.The formation of Cu_(2)(OH)_(3)NO_(3) nanorings has a close relation with OP-10.Transmission electron microscopy(TEM),field emission scanning electron microscopy(FESEM),thermogravimetric analysis(TGA)and X-ray diffractometry(XRD)were used to characterize the obtained nanorings.The UV-Vis spectrum shows that the optical property of Cu_(2)(OH)_(3)NO_(3) nanorings is similar to that of CuO or CuS.The synthesis method used here proves both simplicity and high efficiency.

One-dimensional Copper（Ⅱ） Complex Constructed with Nitrate Counter-anion as Bitopic Connector

Coordination polymer {[Cu（NPPCA）3（NO3）（H20）]-NOyH20}n 1 （ NPPCA = N-（4＇- nitrophenyl）-4-pyridinecarboxamide） has been synthesized by the reaction of NPPCA with copper（H） nitrate in ethanol-water solution and characterized by X-ray diffraction. 1 crystallizes in the monoclinic space, group P21/n, a = 17.341（6）A, b = 6.744（2）A, c = 34.555（12）A, β = 100.493（6）°, V = 3974（2） A^3, Z = 4. Each copper（H） ion has a distorted octahedral coordination geometry. Nitrate anion adopts the unusual coordination mode linking two adjacent copper（H） ions to form a one-dimensional coordination polymer and these chains are further linked by noncovalent interactions.

Efficient electrocatalytic reduction of nitrate to ammonia at low concentration by copper-cobalt oxide nanowires with shell-core structure

Electrocatalytic nitrate reduction to ammonia(NO3−RR)for removing nitrate from wastewater is a promising but challengeable technology that is increasingly studied.Herein,we developed an efficient CuO_(x)and CoCuO_(x)composed hybrid catalyst(CoCuO_(x)@CuO_(x)/copper foam(CF)),characteristic of distinctive shell-core nanowires grown on CF substrate with CuO_(x)core and CoCuO_(x)shell.The built-in electric field formed at the interface of the CoO/Cu_(2)O heterostructure promotes NO3−adsorption by modulating the charge distribution at the interface,which greatly improves the ammonia yield rate and Faradaic efficiency.At−0.2 V vs.reversible hydrogen electrode(RHE),CoCuO_(x)@CuO_(x)/CF achieves not only an excellent ammonia yield rate of up to 519.1μg·h^(−1)·cm^(−2)and Faradaic efficiency of 99.83%at 1 mM NO3−concentration,but also excellent mechanical stabilities.This study provides a novel pathway to design electrocatalyst for the removal of nitrate from dilute nitric acid solutions(≤2 mM).

Determination of Nitrate and Nitrite Contents of Syrian White Cheese

The levels of nitrate and nitrite were determined in 102 samples of Syrian white cheese which represents the major production of total cheeses, manufactured mainly from cow’s milk and sheep’s milk in a less degree. Determination of nitrate and nitrite levels has been made by spectrophotometric method. The results for nitrate in cow’s and sheep’s milk cheeses reveal an average of 5.10 and 6.25 mg/kg, respectively. The results for nitrite in cow’s and sheep’s milk cheese were found to contain 1.24 and 1.31 mg/kg as an average, respectively. Several factors can play a role in the interpretation of the high nitrate content, such as livestock nutrition by forge with high nitrate load and water contaminated with nitrogen fertilizer and domestic effluents, primitive production techniques in many cases, and adding nitrate salts to prevent the growth of gas-producing bacteria caused by failing in the hygienic conditions. There is a necessity to apply strict controls to reduce the presence of these two anions in the Syrian white cheese.

铜基材料电催化还原硝酸盐制氨研究进展

人类工农业活动导致环境中硝酸盐浓度升高,利用电催化技术将硝酸盐还原合成氨(NO_(3)RA)符合“双碳”政策,可达到去除硝酸盐污染和制备氨(NH_(3))的双重目的。该文综述了铜(Cu)基材料电催化硝酸盐还原的反应机理,从反应机理角度分析了不同Cu基催化材料优势性能的起源。围绕Cu单原子、单金属Cu、Cu基合金、Cu基氧化物和Cu基金属有机框架材料的大量研究实例,对不同Cu基催化材料催化NO_(3)RA反应的性能进行归纳总结。通过对Cu基材料催化NO_(3)RA反应影响因素的分析,针对目前存在的问题展开探讨,以期为未来Cu基催化剂电催化NO_(3)RA反应的开发与实际应用提供参考。

Self-supported porous copper oxide nanosheet arrays for efficient and selective electrochemical conversion of nitrate ions to nitrogen gas

Electrochemical techniques have shown advantages for the removal of low-concentration nitrate.Here,copper oxide nanosheets were grown on self-supporting nickel foam(NF)to prepare electrodes(CuO/NF),which realized the rapid and highly selective conversion of nitrate pollutants in sewage into nontoxic and harmless N_(2).The CuO/NF afforded 100%NO_(3)^(-)removal within 100 min and 99.53%selectivity for N_(2)at-50 mA without producing a lot of by-products(NO_(2)-,NH_(4)^(+),and N_(2)H_(4)).Furthermore,81.8%of NO_(3)^(-)was removed under the given conditions after six experimental repetitions.These results suggest that the cat-alyst has excellent electrochemical stability.The performance of CuO/NF for the electrocatalytic removal of NO_(3)^(-)in simulated wastewater(which contained Cl^(-) and SO_(4)^(2-))was almost unaffected.Because of the high efficiency,high stability,and low cost of CuO/NF,this catalyst is practical for the removal of nitrate for wastewater purification.

Copper Nitrate-Mediated Selective Bond Cleavage of Alkynes:Diverse Synthesis of Isoxazoles

An unprecedented copper nitrate-mediated bond cleavage of alkynes was developed for the modular synthesis of isoxazoles,where either C—S bond or C≡C triple bond was cleaved selectively.Substituents attached to the C≡C triple bonds could differentiate the chemical bonds cleavage and reaction pathways disparately.Various transformations of products illustrate promising applications of the given protocols.

Intensification of bituminous coal and lignite oxidation by copper-based activating additives

The oxidation of lignite and bituminous coal samples modified by 5 wt%(in terms of dry salt)addition of copper salts Cu(NO_(3))_(2),CuSO_(4),and Cu(CH_(3)COO)_(2) was studied.The samples’reactivity was studied by thermogravimetry within a temperature range of 45–600℃ at a heating rate of 2.5℃/min in an oxidizing environment.The introduction of activating additives has resulted in a significant decrease in the temperature of intense oxidation onset(ΔT_(i)=20/94℃),in a reduction in the sample residence time in the volatile matter release region(Δt_(e)=2/22 min)and the total duration of the coal combustible mass oxidation(Δt_(f)=8/14 min).The Friedman method was used to calculate the activation energy values for the oxidation process of the modified samples.The maximum change in activation energy values was observed for the bituminous coal sample.The possible mechanism behind the action of the copper-salt additives,which activate the oxidation of lignite and bituminous coal,is discussed.According to the data of mass spectrometric analysis,the concentration of NOx in the reaction products decreases as the temperature of the activated oxidation process is shifted towards the low-temperature region.

氨气沉淀法制备碱式硝酸铜及其形貌机理研究

本文以硝酸铜为原料,采用氨气沉淀法制备了多种形貌的碱式硝酸铜。研究了反应过程中温度、通氨时间和通氨速率对产品微观形貌和产品收率的影响,在最佳反应条件,即反应时间40 min、反应温度90℃、通氨速率500 mL/min时,产品收率达到50%,产品形貌为类六方片状,分散性好,粒径分布接近于正态分布。在产品中发现由纳米级碱式硝酸铜颗粒紧密排布而成的二维纳米网状结构,上面分布有纳米级微孔。采用Morphology及CASTEP程序对碱式硝酸铜生长习性进行理论分析,计算结果与实验吻合,由温度引起的(001)晶面显露程度变化是导致宏观形貌不规则的重要因素。

富含缺陷的Cu@CuTCNQ复合材料增强电催化硝酸盐还原成氨

将硝酸盐(NO_(3))电化学转化为化学原料和燃料氨(NH3),有助于可持续地缓解当前严峻的能源和环境危机.然而,电催化NO_(3)^(-)还原成NH_(3)(NRA)涉及一个缓慢的八电子转移过程,并与水系中的析氢反应(HER)相竞争,这给开发高选择性的NRA催化剂带来巨大挑战.铜基催化剂是最有应用前景的非贵金属催化剂之一,被广泛用于电化学NO_(3)还原研究.然而,块体铜通常表现出较低的NH_(3)选择性且伴随HER竞争反应.近年来,原位表征技术的快速发展使人们能够观察到电解过程中催化剂的结构演变,并验证原位生成的新的高活性相和局部结构(如应变、空位和晶面)在触发高效催化反应中的作用.研究表明,缺陷位点不仅表现出独特的电子特性,而且可以调节相邻原子的电子结构,通过形成新的协同配位结构,来增强化学吸附和改变中间体能垒从而达到最佳性能,已被广泛应用于氧析出、氧还原和二氧化碳还原等电催化反应中.因此,通过结构演化构建富含铜空位缺陷的催化剂,有望提高NRA的活性和选择性.然而,金属表面缺陷工程对电催化反应的影响研究较少,相关反应机理仍不清楚.因此,阐明空位缺陷对NRA的影响和反应机理对于开发高效NRA催化剂具有重要的指导作用.本文通过简单的原位电化学重构方法构建了一种高效的富含铜空位缺陷的铜@四氰基对苯醌二甲烷铜(Cu@CuTCNQ)复合催化剂,用于常温常压NRA反应.X射线衍射精修结果联合X射线吸收光谱表征表明,成功合成了CuTCNQ络合物,其中单分散的金属离子Cu的氧化态为+1价,与N元素配位成键.采用非原位扫描电子显微镜结合原位电化学拉曼光谱研究了NRA过程中CuTCNQ的形貌和结构演变,C-CN拉曼峰发生蓝移表明从CuTCNQ基底到衍生的Cu位点间的电荷转移作用加强.高分辨透射电子显微镜结合电子顺磁共振表征结果表明,衍生的Cu位点表面存在丰富的Cu空位缺陷.丰富的Cu空位缺陷和优化的电荷转移特性使催化剂性能得以提升,在含有0.1 molL^(–1)NO_(3)^(-)的0.1 molL^(–1)KOH溶液中,Cu@CuTCNQ催化剂在-0.6 V vs.RHE还原电位下NRA反应表现出96.4%法拉第效率和144.8μmol h^(–1)cm^(–2)的氨产率,优于结晶性良好的Cu纳米颗粒和大多数Cu基催化剂.利用在线微分电化学质谱对NRA过程的重要中间体NO*和NO_(2)*进行检测,并联合理论计算推测反应途径.结果表明,Cu空位的引入改变了Cu表面的电荷分布,增强了Cu活性位点对NO_(3)^(-)的吸附,降低了电势决速步反应能垒,从而使得NRA的脱氧和加氢过程在热力学上更有利.同时,富含Cu空位缺陷的表面有利于抑制析氢竞争反应,二者共同增强了NRA的活性和选择性.综上,本文突出了通过原位电化学重构策略构建高效NRA催化剂的重要性,并提供了对金属空位-活性依赖性关系的基本理解.

多级结构羟基硝酸铜纳米酶的制备及其对酚类污染物的降解

漆酶是一种多铜氧化酶,在空气条件下即可催化氧化多胺、多酚类有机物,被认为是水处理及土壤修复领域的绿色催化剂。纳米酶是一种具有酶催化活性的纳米材料,因其具有多功能性、低成本、高稳定性等优点,近年来引起广泛关注。因此,本文以尿素水解过程中产生的异氰酸根离子为模板剂,与Cu(NO_(3))_(2)溶液反应制备具有漆酶活性的多级结构羟基硝酸铜[H-Cu_(2)(OH)_(3)NO_(3)]纳米酶。其催化活性是传统Cu(NO_(3))_(2)与尿素水解法制备的羟基硝酸铜的1.85倍,其最大反应速率是漆酶的1.27倍。H-Cu_(2)(OH)_(3)NO_(3)纳米酶在不同pH、温度、储存时间和盐浓度条件下体现良好的催化稳定性。在重复利用12次后,保持58%的催化活性,体现出良好的重复利用性。而且H-Cu_(2)(OH)_(3)NO_(3)纳米酶具有降解土壤与地下水中常见的2,4-二氯苯酚、对苯二酚、2,6-二甲氧基苯酚和邻氨基苯酚等酚类污染物的能力,其降解效率接近甚至优于漆酶。此外,通过对照实验与理论分析,提出H-Cu_(2)(OH)_(3)NO_(3)纳米酶的可能催化机理。

三联吡啶基Cu^(2+)配合物的金属阳离子识别性能研究

采用三联吡啶与硝酸铜在混合溶剂(乙醇与水的比例=9∶1,体积比)常温下反应合成配合物,以该配合物为探针,通过荧光光谱法和紫外光谱法研究该探针的离子识别性能,同时进行干扰实验和检测限的测定。实验结果表明,荧光光谱可以识别Zn^(2+),Zn^(2+)的检测限为1.023×10^(-8)mol/L,探针L和Zn^(2+)的络合比为2∶1。紫外法可识别Bi^(3+),并且其他离子对其干扰都很弱,Bi^(3+)的检测限为3.538×10^(-8)mol/L,探针L和Bi^(3+)的络合比为1∶2。

碱式硝酸铜的制备及催化氧化四氢糠醇的性能

以工业硝酸铜和NaOH为原料,采用简单水热法制备了碱式硝酸铜,将其作为催化剂催化氧化四氢糠醇(THFA),利用FTIR,SEM,XRD,TG,XPS等方法对碱式硝酸铜的结构进行了表征。表征结果显示,所得碱式硝酸铜为高纯度晶体,呈颗粒状、晶体形貌良好。考察了反应条件对碱式硝酸铜催化氧化THFA的影响。实验结果表明,催化氧化150 mL THFA适宜的条件为:催化剂用量2.5 g、140℃、4 MPa、搅拌转速300 r/min。在该条件下,合成丁二酸戊基四氢糠醇酯的选择性为91.794%,转化率为65.67%。碱式硝酸铜催化剂具有良好的稳定性,循环5次后,THFA转化率基本不变,选择性大于80%,为合成四氢糠醇酯提供了一条方便绿色的途径。

甘氨酸-硝酸盐燃烧合成制备铜/铁基纳米催化剂及表征

以硝酸铜与硝酸铁为主要原料,甘氨酸为络合剂和燃烧剂,运用甘氨酸-硝酸盐燃烧法合成了铜/铁基催化剂纳米粒子。讨论了不同甘氨酸/氮质量比对合成的影响,通过X射线衍射仪、透射电子显微镜、热分析仪和扫描电子显微镜对制备的材料进行了结构及性能表征,考察了其在有机污染物上的催化性能。

铜/石墨烯新型电化学传感器检测性能的研究

检测水中硝酸根离子和亚硝酸根离子浓度的方法很多,如高效液相色谱、分光光度计、色分析法等。电化学传感器凭借响应速度快、灵敏度高、选择性好等优点成为检测新技术的研究热点之一。很多研究表明,由石墨烯纳米复合功能材料构建的新型电化学传感器性能优异。基于此,一种铜负载于石墨烯表面的纳米材料在室温下被合成,并通过扫描电子显微镜、透射电镜、原子力显微镜和电化学阻抗谱等多种方法对其进行了表征。由该材料制备的一种新型电化学传感器,其检测性能运用循环伏安法和微分脉冲伏安法进行了探究。结果表明:该传感器对硝酸根离子和亚硝酸根离子检测性能好,检测浓度范围宽,由0.1μmol/L到100μmol/L;检出限低:硝酸根离子检出限为0.03μmol/L,亚硝酸根离子检出限为0.05μmol/L。所制备的传感器对实际样品进行了检测,结果令人满意,证明新型电化学传感器具有实际使用价值。

用Pd-Cu-Pt/γ-Al_2O_3催化剂还原水中的硝酸盐

以自制的高纯γ Al2 O3 为载体 ,用双浸渍法制备了不同Pd/Cu比的Pd Cu/γ Al2 O3 催化剂 ,在间歇式反应器中直接处理含硝酸盐废水 .结果表明 ,利用不同Pd/Cu比的Pd Cu/γ Al2 O3 催化剂及Pd Cu Pt/γ Al2 O3 催化剂 ,同时用甲酸为 pH调节剂 ,在适合的条件下 ,于 4 0min内就能达到脱除硝酸盐的目的 ,氮脱除率可达 95 % .这有可能发展成为一项有效和实用的水处理技术 ,特别是在以地下水作为饮用水源的农村地区 .

钯-铜负载活性炭催化还原去除水中硝酸盐研究

通过以活性炭载体浸渍负载钯铜双金属制备的催化剂,利用半连续试验,研究了活性炭载体双金属催化剂对水中硝酸盐的催化还原去除的特点和规律。结果表明,在负载钯/铜原子比为1:1、金属负载量Pd质量分数为1.2%、Cu质量分数为0.72%时,催化剂具有最佳的活性与选择性;最佳H2流量为100 mL.min-1,此时催化反应进行迅速,选择性较好;溶液pH过高或者过低对催化剂活性和选择性都有不利影响,适宜的溶液pH控制范围为4.5～5.5;对于初始质量浓度为100 mg.L-1的硝酸盐溶液,反应时间为2 h时,硝酸盐去除率可达96%以上,氨氮生成率为22%。