水滑石负载的钯纳米粒子对水合肼的电催化氧化

利用共沉淀方法制备了载体水滑石(LDH), 通过离子交换法将PdCl2₄^- 插入水滑石层间, 再用水合肼将其还原, 制备得到了水滑石负载的分散状钯纳米粒子(LDH-Pd⁰). 利用X射线衍射(XRD)、透射电镜(TEM)和X射线电子能谱(XPS)等手段对所得样品进行了表征, 结果表明钯纳米粒子能很好地分散在水滑石上. 将该纳米材料修饰的玻碳电极(GCE)用于水合肼的电催化氧化, 该修饰电极表现出很好的电化学催化活性. 用循环伏安法(CV)、计时库仑法(CC)和计时安培法(i-t)对修饰电极的催化活性、有效表面积和水合肼的催化氧化机理等进行了研究. 结果表明水合肼在-0.1 V附近有明显的氧化峰, 在1.0×10^-5-2.0×10^-4 mol·L^-1范围内, 阳极峰电流与水合肼浓度间有良好的线性关系, 其检测限为9.5×10^-7 mol·L^-1. 计算得到GCE, LDH-Pd⁰/GCE 和LDH/GCE电极活化面积分别为0.02089, 0.02762 和0.02496 cm². 推知水合肼的氧化过程有4 电子和4 质子参与, 并且其在电极上的反应是受扩散控制的不可逆过程.     

Electrocatalytic Behavior of Manganese and Cobalt Porphyrins Attached to Graphene Quantum Dots: Applied in the Oxidation of Hydrazine

Manganese and cobalt metalated 5, 10, 15-tris(aminophenyl)-20-(4-carboxyphenyl) porphyrins (ClMnTA₃CPP and CoTA₃CPP) were synthesized and attached to graphene quantum dots (GQDs) via π-π interaction and electrostatic interaction. The electrochemical oxidation of hydrazine was performed via cyclic voltammetry and chronoamperometry. The CoTA₃CPP showed good electrocatalytic activity towards the oxidation of hydrazine in terms of catalytic rate constants and limits of detection (LoD). ClMnTA₃CPP showed lower overpotential 0.60 V. The introduction of GQDs improved the electrocatalytic ability when combined with CoTA₃CPP and ClMnTA₃CPP with the lowest LoD (0.0025 mM CoTA₃CPP–GQDs) followed by ClMnTA₃CPP–GQDs with 0.0033 mM.     

Electrocatalytic Determination of Traces of Hydrazine by a Glassy Carbon Electrode Modified with Palladium‐Gold Nanoparticles

A glassy carbon electrode modified with palladium/gold nanoparticles was successfully prepared by an electrodeposition process. It efficiently oxidizes hydrazine at a low overpotential of ?0.26 V versus SCE. The Pd‐AuNPs with an average size of 50–80 nm are uniformly dispersed at the GCE. The Pd‐AuNPs/GCE was used for determination of hydrazine in phosphate buffer solution of pH 7.0. The amperometric current response of the electrode was increased linearly over a hydrazine concentration of 0.1–500 µM with a limit of detection of 0.07 µM .The prepared hydrazine sensor exhibited high sensitivity, good selectivity reproducibility and long term stability.     

Functionalization of Reduced Graphene Oxide with β‐cyclodextrin Modified Palladium Nanoparticles for the Detection of Hydrazine in Environmental Water Samples

A sensitive and selective hydrazine sensor was developed by β‐cyclodextrin modified palladium nanoparticles decorated reduced graphene oxide (PdNPs‐β‐CD/rGO) nanocomposite. The PdNPs‐β‐CD/rGO hybrid material was prepared by simple electrochemical method. The hydrophobic cavity of β‐CD ineracts with palladium nanoparticles by hydrophobic interaction and further it is uniformly assembled on the rGO surface through hydrogen bond formation, which is clearly confirmed by FT‐IR, FESEM and TEM. The high electrocatalytic activity of hydrazine oxidation was observed at −0.05 V (vs. Ag/AgCl) on PdNPs‐β‐CD/rGO modified electrode; due to the excellent stabilization, high catalytic activity and large surface area of the PdNPs‐β‐CD/rGO composite. The PdNPs‐β‐CD/rGO fabricated hydrazine sensor exhibited an excellent analytical performance, including high sensitivity (1.95 μA μM⁻¹ cm⁻²), lower detection limit (28 nM) and a wide linear range (0.05 to 1600 μM). We also demonstrated that the PdNPs‐β‐CD/rGO nanocomposite modified electrode is a highly selective and sensitive sensor towards detection of hydrazine among the various interfering species. Hence, the proposed hydrazine sensor is able to determine hydrazine in different water samples.     

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine in Industrial Boiler Feed Water Using a Cobalt Phthalocyanine-modified Electrode

Abstract

A carbon paste electrode modified with cobalt phthalocyanine (CPECoPc) was developed and applied to the determination of hydrazine [N₂H₄] in industrial boiler feed water. The CPECoPc exhibited good electrocatalytical activity for hydrazine oxidation at pH 13. A linear correlation was obtained between anodic peak current (I_ap) and hydrazine concentration in the range of 1.25 × 10^?4 to 9.80 × 10^?4 mol L^?1, fit by the equation I_ap = 1.47 + 4.90 × 10⁵ [N₂H₄] with a correlation coefficient of 0.9967. A detection limit of 7.35 × 10^?5 mol L^?1 was obtained. Recovery of hydrazine from three samples ranged between 99.0% and 102.9%. The modified electrode showed no interference by cations commonly present in boiler water, such as K⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Pb²⁺, and Zn²⁺. The results obtained for hydrazine in boiler water using the proposed modified electrode are in agreement with the data obtained by a standard spectrophotometric method, at the 95% confidence level.     

New Electrocatalytic Reactions at a Mercury Electrode in the Presence of Homocysteine or Cysteine and Cobalt or Nickel Ions

Homocysteine (Hcy) and cysteine (Cys) mercury thiolate layers were prepared by anodic polarization of a mercury electrode in amino acid containing solutions and then investigated in the cathodic regime in the presence of Ni²⁺ or Co²⁺ ions. The sulfhydryl function in the mercury thiolate undergoes a slow disintegration resulting in surface‐attached mercury sulfide. During the cathodic scan, Hg²⁺ substitution by Ni²⁺ or Co²⁺ yields minute amounts of the relevant metal sulfide. Such a species catalyzes hydrogen evolution at ?1.3 V vs. Ag|AgCl|KCl(3 M). Hcy experiences a faster decomposition and, consequently, displays a stronger catalytic effect. Each compound catalyzes the reduction of Ni²⁺ or Co²⁺, but only Cys (bound in metal complexes) induces typical catalytic hydrogen evolution processes such as the Brdi?ka reaction (with Co²⁺; pH around 9), or the catalytic hydrogen prewave (CHP) (with Ni²⁺; pH near 7). On the other hand, Hcy catalyzes the hydrogen evolution in the presence of Co²⁺ at ?1.5 V in the same way than sulfur derivatives with no amine function do. Metal sulfide formation does not interfere with CHP and Brdi?ka processes. Correlations between the physical state of the metal sulfide (adsorbed molecule or aggregate form) and its catalytic properties are discussed and possible analytical applications suggested.     

Electrocatalytic Oxidation of Diethylaminoethanethiol and Hydrazine at Single‐walled Carbon Nanotubes Modified with Prussian Blue Nanoparticles

In this work, edged plane pyrolytic graphite electrode EPPGE was modified with functionalised single‐walled carbon nanotubes and Prussian blue nanoparticles (PB). The modified electrode was characterised by techniques such as TEM, FTIR, XPS, EDX and cyclic voltammetry. The EPPGE‐SWCNT‐PB platform exhibited enhanced electron transport and catalytic efficiency towards the oxidation of Diethylaminoethanethiol (DEAET) and hydrazine compared with the other electrodes studied. The EPPGE‐SWCNT‐PB showed good electrochemical stability in the analytical solution, showing limit of detection in the micromolar range and catalytic rate constant of 3.71×10⁶ and 7.56×10⁶ cm³ mol^?1 s^?1 for DEAET and hydrazine respectively. The adsorption properties of these analytes that impact on their detection at the SWCNT‐PB film modified electrode were evaluated and discussed.     

Electrochemical Detection of Hydrazine Based on Electrospun Palladium Nanoparticle/Carbon Nanofibers

In this work, we developed an electrochemical method for the detection of hydrazine based on palladium nanoparticle/carbon nanofibers (Pd/CNFs). Pd/CNFs were prepared by electrospinning technique and subsequent thermal treatments. The electrocatalytic behaviors of Pd/CNFs modified glassy carbon electrode (Pd/CNF‐GCE) for hydrazine oxidation were evaluated by cyclic voltammetry (CV), an obvious and well‐defined oxidation peak appeared at ?0.32 V (vs. Ag/AgCl). The mechanism of the oxidation of hydrazine at Pd/CNF‐GCE was also studied, which demonstrated an irreversible diffusion‐controlled electrode process and a four‐electron transfer involved in the overall reaction. Furthermore, the wide linear range, low detection limit, good reproducibility and excellent storage stability were obtained utilizing differential pulse voltammetry (DPV).     

Facile Synthesis of Pd Nanoparticle Modified Carbon Black for Electroanalysis: Application to the Detection of Hydrazine

Carbon black nanoparticles modified with palladium nanoparticles (Pd/CB) were prepared using a facile methodology. Stirring CB in an aqueous solution of palladium chloride was found to result in the spontaneous formation of Pd nanoparticles on the CB surface. The Pd/CB composite demonstrated high electrocatalytic activity towards hydrazine oxidation, with good stability and reproducibility. Three linear dynamic ranges of hydrazine determination were found between 5 µM and 50 mM. The limit of detection (LOD) for hydrazine was found to be 8.8 µM (based on 3σ). The sensitivity of unmodified CB to trace metal impurities present in certain common electrolytes is also noted.     

有序介孔碳载钯的制备、表征及对甲酸的电催化氧化性能

通过浸渍法和硫引入贵金属法分别制备了主要负载在介孔碳主孔道(MPC/Pd-1)和负载在介孔碳孔壁上小介孔中[MPC/(S)Pd-2]的两类负载型钯电催化剂, 用XRD, SEM, TEM和电化学等方法表征了其结构和电催化性能. 循环伏安结果表明, 有序介孔碳载钯催化剂MPC/Pd-1和MPC/(S)Pd-2对甲酸氧化的催化活性分别是商用钯黑催化剂的4.0和2.4倍. MPC/Pd-1中的钯位于介孔碳的主孔道上, 增加了催化剂/电解质/反应物三相界面的面积, 使得其比MPC/(S)Pd-2的催化活性更高.     

Gold Nanoparticles Decorated Graphene as a High Performance Sensor for Determination of Trace Hydrazine Levels in Water

Electrochemical sensors provide a selective, sensitive and an easy approach to detect hazardous substances such as hydrazine. Herein, we investigate a facile route for the fabrication of a nanostructured composite based on Au nanoparticles (AuNPs) decorated graphene and present its sensing performance towards hydrazine. Our strategy involves electrophoretic deposition (EPD) of graphene oxide (GO) on Au substrate to obtain a uniform layer EPD‐GO, followed by electrochemical reduction of GO to yield high quality graphene ERGO and electrodeposition of monodispersed AuNPs on ERGO (AuNPs/ERGO/Au). The modified AuNPs/ERGO/Au electrode was characterized using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT‐IR) techniques. The sensor exhibited an improved catalytic activity with a peak potential of +87 mV (vs. Ag/AgCl) for hydrazine oxidation. The high performance of this hybrid electrode is due to the presence of a synergistic effect between AuNPs and ERGO at their interface. Insights into the mechanism and kinetics of hydrazine oxidation are withdrawn from varying the voltage scan rate as the reaction is fully irreversible and diffusion‐controlled. The proposed hydrazine sensor showed suitability for nanomolar detection (detection limit of 74 nM), high selectivity in the presence of common ions and efficiency for application in water samples.     

Synthesis of MnO2/MWNTs Nanocomposites Using a Sonochemical Method and Application for Hydrazine Detection

A sonochemical method has been successfully used to synthesize MnO₂/MWNTs nanocomposites. The structure and nature of the resulting MnO₂/MWNTs composite were characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray diffraction (EDX), X‐ray photoelectron spectroscopy (XPS).The results show that the sonochemically synthesized MnO₂ nanoparticles were homogeneously dispersed on the modified MWNT surfaces. The performance of the MnO₂/MWNTs nanocomposites modified electrode was characterized using cyclic voltammetry (CV) and Nyquist plots. The electrode exhibits efficient electron transfer ability and high electrochemical response towards hydrazine. This may be attributed to the small particle size, high dispersion of MnO₂ particles. The fabricated hydrazine sensor showed a wide linear range of 5.0×10^?7–1.0×10^?3 M with a response time less than 5 s and a detection limit of 0.2 μM. Taking the advantage of the unique properties of both MWNTs and MnO₂, it would greatly broaden the applications of MWNTs and MnO₂.     

Division Electrosynthesis of Palladium Nanomaterials with Copper–Graphene as Sacrificial Templates and Its Application for Hydrazine Sensing

One‐pot electrodeposited copper‐graphene (Cu‐GE ) nanocomposite acting as sacrificial template for the division electrosynthesis of palladium nanoparticles (PdNPs ) on pyrolytic graphite electrode (PGE ) was synthesized. The designed PdNPs‐GE nanocomposite was evaluated as a new material for highly sensitive determination of hydrazine (N₂H₄ ). Scanning electron microscopy revealed that the PdNP‐GE ‐modified PGE had uniform morphology. The results of energy‐dispersive X‐ray spectrograms confirmed the ingredients of the division electrosynthesis process. Electrochemical experiments were performed to characterize the sensing properties of PdNPs‐GE toward the electrocatalytic oxidation of N₂H₄ at 0.20 V in sodium phosphate buffered saline (0.1 M pH 7.0). The sensor showed fast response (<3 s), high sensitivity [398 (1 × 10⁻⁶ A) (1 × 10⁻³ M)⁻¹], and broad linearity in the range 2.5 × 10⁻⁸–2.7 × 10⁻⁴ M with a relatively low detection limit of 1.0 × 10⁻⁸ M (S/N = 3).     

纳米Pd上H2O2的电催化还原反应

利用纳米Pd颗粒修饰的Au旋转圆盘电极, 通过强制对流条件下的线性电势扫描伏安法, 研究了酸性介质中H2O2在纳米Pd催化剂上的电还原反应. 动力学研究结果表明, H2O2在纳米Pd上电还原反应的表观活化能为27.6 kJ·mol-1, 反应为2电子转移过程, 电解质的阴离子类型显著影响纳米Pd对H2O2电化学还原反应的催化性能. 根据动力学电流与H2O2浓度及与H+浓度的关系, 提出了Pd催化H2O2电还原反应可能的速率控制步骤, 并讨论了其可能的反应机理.     

Palladium nanoparticle decorated carbon ionic liquid electrode for highly efficient electrocatalytic oxidation and determination of hydrazine

In this work arrays of palladium nanoparticles were synthesized on carbon ionic liquid electrode (CILE) (Pd/CILE), and the electrocatalytic oxidation of hydrazine was investigated using this electrode. Electrochemical oxidation of hydrazine in phosphate buffer (pH 7) was performed using cyclic voltammetry and square wave voltammetric techniques (SWV). Using the proposed electrode, a highly reproducible and well-defined peak was obtained for hydrazine at a very low potential of −0.02 V versus Ag/AgCl. A linear dynamic range of 5-800 μM with an experimental detection limit of 0.82 μM was obtained. These results show that the proposed electrode displays better electrocatalytic activity compared to the previously reported palladium modified electrodes towards oxidation of hydrazine.     

硅量子点支撑钯纳米粒子的可控制备

采用微乳法制备烯丙胺修饰的硅量子点(Si QDs),通过紫外-可见吸收光谱、荧光光谱和红外光谱对其光学性能进行了表征,通过透射电镜(TEM)对其形貌进行了表征,测得其荧光量子产率为10.06%,荧光寿命τ1=3.1982ns,τ2=12.4527ns。依据Si QDs的光学性质,制备了Si QDs支撑Pd纳米粒子材料(Si QDs/Pd)。通过量子点的浓度实现了Pd纳米粒子形貌和尺寸的有效控制。结果表明制备的Pd纳米材料具有较好的分散性,在有机催化和能源转化领域具有潜在的应用价值。     

Porphyrin Nanorods Modified Glassy Carbon Electrode for the Electrocatalysis of Dioxygen,Methanol and Hydrazine

Porphyrin nanorods (PNR) were prepared by ionic self‐assembly of two oppositely charged porphyrin molecules consisting of free base meso‐tetraphenylsulfonate porphyrin (H₄TPPS₄^2?) and meso‐tetra(N‐methyl‐4‐pyridyl) porphyrin (MTMePyP⁴⁺M=Sn, Mn, In, Co). These consist of H₄TPPS₄^2?? SnTMePyP⁴⁺, H₄TPPS₄^2?? CoTMePyP⁴⁺, H₄TPPS₄^2?? InTMePyP⁴⁺ and H₄TPPS₄^2?? MnTMePyP⁴⁺ porphyrin nanorods. The absorption spectra and transmission electron microscopic (TEM) images of these structures were obtained. These porphyrin nanostructures were used to modify a glassy carbon electrode for the electrocatalytic reduction of oxygen, and the oxidation of hydrazine and methanol at low pH. The cyclic voltammogram of PNR‐modified GCE in pH 2 buffer solution has five irreversible processes, two distinct reduction processes and three oxidation processes. The porphyrin nanorods modified GCE produce good responses especially towards oxygen reduction at ?0.50 V vs. Ag|AgCl (3 M KCl). The process of electrocatalytic oxidation of methanol using PNR‐modified GCE begins at 0.71 V vs. Ag|AgCl (3 M KCl). The electrochemical oxidation of hydrazine began at around 0.36 V on H₄TPPS₄^2?? SnTMePyP⁴⁺ modified GCE. The GCE modified with H₄TPPS₄^2?? CoTMePyP⁴⁺ H₄TPPS₄^2?? InTMePyP⁴⁺ and H₄TPPS₄^2?? MnTMePyP⁴⁺ porphyrin nanorods began oxidizing hydrazine at 0.54 V, 0.59 V and 0.56 V, respectively.     

Electrochemical Activation of Graphite Nanosheets Decorated with Palladium Nanoparticles for High Performance Amperometric Hydrazine Sensor

Herein, we have demonstrated a preparation of palladium nanoparticles on electroactivated graphite nanosheets modified screen printed carbon electrode (PdNPs‐EGNS/SPCE) by a simple electrochemical method. The well‐prepared electrocatalyst was potentially applied to the high performance electrocatalytic oxidation of hydrazine in neutral medium. The PdNPs‐EGNS novel composite was characterized by scanning electron microscope (SEM) and the average diameter and thickness of PdNPs and EGNS were found to be ～38 nm and 85 nm, respectively. The high performance electrocatalytic determination of hydrazine was performed by the amperometric i‐t method. The fabricated sensor displayed irreversible electrocatalytic oxidation of hydrazine with diffusion‐controlled electrode process. The oxidation of hydrazine at PdNPs‐EGNS/SPCE showed wider linear range 0.05–1415 µM and high sensitivity 4.382 µA µM^?1 cm^?2. The as‐prepared electrocatalyst achieved quick response towards hydrazine with a lower detection limit 4 nM.     

Acetylferrocene Modified Carbon Paste Electrode; A Sensor for Electrocatalytic Determination of Hydrazine

The electrocatalytic oxidation of hydrazine at a carbon paste electrode spiked with acetylferrocene as a mediator was studied by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. In contrast to other ferrocenic compounds, acetylferrocene exhibits a chemical irreversible behavior, but it can act as an effective mediator for electrocatalytic oxidation of hydrazine, too. The heterogeneous electron transfer rate constant between acetylferrocene and the electrode substrate (carbon paste) and the diffusion coefficient of spiked acetylferrocene in silicon oil were estimated to be about 3.45×10^?4 cm s^?1 and 4.45×10^?9 cm² s^?1, respectively. It has been found that under the optimum conditions (pH 7.5) the oxidation of hydrazine occurs at a potential of about 228 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak current of hydrazine was linearly dependent on its concentration and the obtained linear range was 3.09×10^?5 M–1.03×10^?3 M. The detection limit (2σ) has been determined as 2.7×10^?5 M by cyclic voltammetry. Also, the peak current was increased linearly with the concentration of hydrazine in the range of 1×10^?5 M–1×10^?3 M by differential pulse voltammetry with a detection limit of 1×10^?5 M. This catalytic oxidation of hydrazine has been applied as a selective, simple, and precise new method for the determination of hydrazine in water samples.     

In situ synthesis of ceria nanoparticles in the ordered mesoporous carbon as a novel electrochemical sensor for the determination of hydrazine

A novel ceria (CeO₂)–ordered mesoporous carbon (OMC) modified electrode for the sensitive amperometric determination of hydrazine was reported. CeO₂–OMC composites were synthesized via a hydrothermal method at a relatively low temperature (180 °C) and characterized by scanning electron microscopy (SEM), transmission electron microcopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The CeO₂–OMC modified glassy carbon electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) and indicated good electrocatalytic effect to the oxidation of hydrazine. Under the optimized conditions, the present sensor could be used to measure hydrazine in wide linear range from 40 nM to 192 μM (R² = 0.999) with a low detection limit of 12 nM (S/N = 3). Additionally, the sensor has been successfully applied to detect hydrazine in real water samples and the recoveries were between 98.2% and 105.6%. Eventually, the sensor exhibited an excellent stability and reproducibility as a promising method for determination of hydrazine.