Electrocatalytic Oxidation of Hydrogen Peroxide on Poly(m‐toluidine)‐Nickel Modified Carbon Paste Electrode in Alkaline Medium

The poly(m‐toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO₄, also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m‐toluidine)/modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 μM (S/N=3). The catalytic reaction rate constant, (k_h), was calculated 5.5×10² M^?1 s^?1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.     

Synthesis of PtxSn/MWCNTs and their Application in Non‐enzymatic Glucose and Hydrogen Peroxide Sensors

Pt_xSn/MWCNTs (x=1, 2, 3) nanocomposites were synthesized by chemical reduction. Comparing all of the materials, the results revealed that the best material was Pt₃Sn/MWCNTs. The sensor based on Pt₃Sn/MWCNTs exhibited excellent catalytic activities towards glucose and hydrogen peroxide. Sensing of glucose had a double‐linear range: one was between 50 μM and 550 μM, the other was between 1.35 mM and 16.35 mM. These were due to the fact that more and more intermediate species were adsorbed onto the electrode surface with increasing concentration of glucose, which limited the following glucose oxidation. Meanwhile, the sensor also had a linear response range between 0.05 mM and 18.95 mM for hydrogen peroxide. Furthermore, the glucose and hydrogen peroxide sensors exhibited excellent selectivity, stability, and reproducibility. Thus the sensors had potential utilities in the detection of glucose and hydrogen peroxide.     

Magnetic loading of carbon nanotube/nano-Fe3O4 composite for electrochemical sensing

An electrochemical sensing platform was developed based on the magnetic loading of carbon nanotube (CNT)/nano-Fe₃O₄ composite on electrodes. To demonstrate the concept, nano-Fe₃O₄ was deposited by the chemical coprecipitation of Fe²⁺ and Fe³⁺ in the presence of CNTs in an alkaline solution. The resulting magnetic nanocomposite brings new capabilities for electrochemical devices by combining the advantages of CNT and nano-Fe₃O₄ and provides an alternative way for loading CNT on electrodes. The fabrication and the performances of the magnetic nanocomposite modified electrodes have been described. Cyclic voltammetry (CV) and constant potential measurement indicated that the incorporated CNT exhibited higher electrocatalytic activity toward the redox processes of hydrogen peroxide. In addition, chitosan (CTS) has also been introduced into the bulk of the CNT/nano-Fe₃O₄ composite by coprecipitation to immobilize glucose oxidase (GOx) for sensing glucose. The marked electrocatalytic activity toward hydrogen peroxide permits effective low-potential amperometric biosensing of glucose, in connection with the incorporation of GOx into CNT/Fe₃O₄/CTS composite. The accelerated electron transfer is coupled with surface renewability. TEM images and XRDs offer insights into the nature of the magnetic composites. The concept of the magnetic loading of CNT nanocomposites indicates great promise for creating CNT-based biosensing devices and expands the scope of CNT-based electrochemical devices.     

A Novel Amperometric Transducer Electrode with Iridium‐Niobium Binary Alloys

We have discovered that an Ir‐23Nb binary alloy more effectively oxidizes hydrogen peroxide than Ir, Ir‐13Nb, Ir‐17Nb, Ir‐30Nb, Ir‐43Nb, Ir‐62Nb, or Nb. The oxidation capability was determined via cyclic voltammogram measurements of pH‐buffer and hydrogen peroxide. We ascertained that applying a 0.7 V potential produces hydrogen peroxide currents of 9.2 μA/mm² Ir‐23Nb, 5.3 μA/mm² Ir, 5.1 μA/mm² Ir‐17Nb, 3.7 μA/mm² Ir‐13Nb, 2.0 μA/mm² Ir‐30Nb, 1.5 μA/mm² Ir‐43Nb, 0.6 μA/mm² Ir‐62Nb, and 0.13 μA/mm² Nb. These results indicate that the effective oxidation of Ir‐23Nb for hydrogen peroxide might be due to its fcc+L1₂ two‐phase structure and that Ir‐23Nb can be used as an amperometric transducer material.     

Pt and Pt–Ru nanoparticles decorated polypyrrole/multiwalled carbon nanotubes and their catalytic activity towards methanol oxidation

Conducting polymer composite films comprised of polypyrrole (PPy) and multiwalled carbon nanotubes (MWCNTs) [PPy–CNT] were synthesized by in situ polymerization of pyrrole on carbon nanotubes in 0.1 M HCl containing (NH₄)S₂O₈ as oxidizing agent over a temperature range of 0–5 °C. Pt nanoparticles are deposited on PPy–CNT composite films by chemical reduction of H₂PtCl₆ using HCHO as reducing agent at pH = 11 [Pt/PPy–CNT]. The presence of MWCNTs leads to higher activity, which might be due to the increase of electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces allowing higher dispersion and utilization of the deposited Pt nanoparticles. A comparative investigation was carried out using Pt–Ru nanoparticles decorated PPy–CNT composites. Cyclic voltammetry demonstrated that the synthesized Pt–Ru/PPy–CNT catalysts exhibited higher catalytic activity for methanol oxidation than Pt/PPy–CNT catalyst. Such kinds of Pt and Pt–Ru particles deposited on PPy–CNT composite polymer films exhibit excellent catalytic activity and stability towards methanol oxidation, which indicates that the composite films is more promising support material for fuel cell applications.     

Electrocatalytic Oxidation of Hydrogen Peroxide at a Sol‐gel Derived Carbon Ceramic Electrode Modified with Copper Iodide

A novel modified carbon ceramic electrode using CuI as modifier was fabricated. The copper iodide modified sol‐gel derived carbon ceramic (CIM‐SGD‐CC) electrode has high catalytic ability for electrooxidation of hydrogen peroxide. The charge transfer coefficient (α) and exchange current density (j₀) for the modified electrode were calculated. It has been shown that using the CIM‐SGD‐CC electrode, hydrogen peroxide can be determined by cyclic voltammetry and amperometry with limit of detections 26 and 0.31 μmol L^?1, respectively. The advantages of the modified CCE are its good stability and reproducibility of surface renewal by simple polishing, excellent catalytic activity.     

Study On The Catalytic Reaction Of β-Cd-Hemin Using 2, 3, 4-Trichlorophenol As Substrate And Analytic Application

ABSTRACT|The catalytic activity of various mimetic enzymes instead of the peroxidase have been investigated by 4-aminoantipyrine (4-AAP) and 2, 3, 4-trichlorophenol (TCP) to form a dye utilizing hydrogen peroxide as hydrogen acceptor. The different Chlorophenolic derivatives, which act as a substrate in β-CD-hemin-H₂O₂-4-AAP catalytic reaction, have been systematically studied.|Meanwhile, the relationship of structure-effect for the β-CD-hemin as catalyst, and chlorphenols as substrate has been respectively discussed. The mechanism of catalytic reaction has been investigated. The results showed that β-CD-hemin was the best mimetic enzyme for peroxidase among those tested and TCP was a good substrate for the determination of hydrogen peroxide with β-CD-hemin. The method for the determination of hydrogen peroxide was proposed using 4-AAP-TCP system with β-CD-hemin as catalyst. A linear calibration graph was obtained over the H₂O₂ concentration of 4.8×10-^?8-7.7×10-^?5M, and the relative standard deviation at a H₂O₂ concentration of 2.8×10-^?5M was 2.5%. The apparent molar absorptivity of the chromogenic reaction for H₂O₂ was 1.54× 10⁴ L.mol-^?1.cm^?1. Satisfactory results were obtained in the determination of H₂O₂ in synthetic samples by this method.

Also, the method was coupled with the glucose oxidation reaction to determination glucose in human serum.     

Catalytic determination of molybdenum in plants by flow-injection spectrophotometry with ion-exchange separation

The catalytic effect of molybdenum n the oxidation of iodide by hydrogen peroxide is utilized. A cation-exchange resin column is incorporated into the system to remove interfering ions; during sample processing, the interfering ions are eluted towards waste. Plant materials are ashed and solutions are injected. The proposed system can handle about 40 samples per hour with molybdenum contents in the 1.0–40.0 μg 1^?1 range. Results are precise (r.s.d. usually <%) and in agreement with those obtained by graphite-furnace atomic absorption spectrometry.     

Activation of H2O2 by methyltrioxorhenium(VII) inside β-cyclodextrin

The effect of β-cyclodextrin on the catalytic stability and reactivity of methylrhenium trioxide (MTO), CH₃ReO₃, which has been used for activation of hydrogen peroxide toward oxidation and epoxidation reactions, was studied using UV–Vis spectrophotometery. The stability and reactivity of the new catalytic system (MTO/β-CD) to activate H₂O₂ toward oxidation of indigo blue dye were investigated in basic media. Furthermore, effects of inclusion stoichiometry, temperature and concentrations of hydrogen peroxide on the stability and reactivity of the MTO/β-CD system were investigated. The formation of the inclusion complex between MTO and β-CD was confirmed experimentally using the changes in the UV–Vis absorption spectra. The results of this study demonstrate that the complexation process was better guaranteed when the amount of β-CD is higher than that of MTO, using a 1:2 molar ratio of MTO:β-CD enhances both the activity and stability of the catalyst. The results showed that the stability of the catalytic system was enhanced in presence of β-CD with maintaining good reactivity of the MTO even in the presence of high concentration of NaOH. The changes of thermodynamic activation parameters (ΔH^≠ and ΔS^≠) for the oxidation reaction of indigo with H₂O₂ catalyzed by MTO/β-CD system were determined on the basis of the experimental data.     

Development of Nonenzymatic Hydrogen Peroxide Sensor Based on Successive Pd‐Ag Electrodeposited Nanoparticles on Glassy Carbon Electrode

A novel strategy to fabricate hydrogen peroxide (H₂O₂) sensor was developed by electrodepositing palladium? silver nanoparticles (NPs) on a glassy carbon electrode. The morphology of the modified electrode was characterized by Scanning electron microscopy (SEM). The result of electrochemical experiments showed that such constructed sensor had a favorable catalytic ability, high sensitivity, excellent selectivity towards reduction of hydrogen peroxide (H₂O₂). The response to H₂O₂ is linear in the range between 0.30 μM to 2.50 mM, and the detection limit is 0.1 μM (at an S/N of 3).     

The effect of encapsulated Zn-POM on the catalytic activity of MIL-101 in the oxidation of alkenes with hydrogen peroxide

Zinc monosubstituted Keggin heteropolyanion [PZnMo₂W₉O₃₉]^5? was electrostatically bound to nanocages of MIL-101 polymer matrix. The Zn-POM@MIL-101 catalyst was characterized by XRD, N₂ adsorption, atomic absorption (AAS), and FT-IR spectroscopic methods. The catalytic activity of the new composite material, Zn-POM@MIL-101, was assessed in the oxidation of alkenes using aqueous hydrogen peroxide as oxidant. Zn-POM@MIL-101/H₂O₂ catalytic system demonstrated good catalytic activity in the oxidation reactions. Zn-POM@MIL-101 was reusable for three catalytic cycles. While the MIL-101 matrix is an active catalyst in these oxidation reactions, the presence of Zn-POM significantly changed the selectivity and reaction times.     

可见光辐射下活性炭-铁酸镍杂化催化剂光催化氧化氨氮

铁酸镍（NiFe₂O₄）中的镍原子抑制其光芬顿催化活性. 然而,活性炭（AC）能激活其光芬顿催化活性,结果导致复合催化剂AC-NiFe₂O₄在过氧化氢存在时可见光辐射下也可催化氧化氨氮. 用X射线衍射（XRD）,透射电镜（TEM）,傅里叶变换红外（FTIR）光谱,紫外-可见漫反射光谱（UV-Vis DRS）,比表面积和振动样品磁强计对催化剂进行了表征. 光催化降解氨氮的实验表明,该复合催化剂在10 h内氨氮的降解率可达到91.0%,而同样条件下没有催化剂时氨氮的去除率只有24.0%. 对照实验表明,裸铁酸镍在可见光辐射下,氨氮的降解率只有30.0%. 这表明活性炭加速了氨氮的氧化速率. 动力学研究表明,氨氮的氧化遵循一级反应动力学规律,其表观反应动力学常数为3.538×10^-3 min^-1. 机理研究表明,氨氮的氧化是通过生成HONH₂ 中间体,然后转化为NO₂^- .8次循环实验表明该复合催化剂容易分离、可循环使用、且催化活性十分稳定. 因此,该催化剂具有潜在的应用价值.     

碳纳米管负载的Pd-Ag-Sn催化剂对甲酸的电氧化

采用硼氢化钠还原的方法合成了碳纳米管负载的钯基纳米催化剂（Pd/CNT,Pd₇Ag₃/CNT,Pd₇Sn₂/CNT,Pd₇Ag₁Sn₂/CNT,Pd₇Ag₂Sn₂/CNT和Pd₇Ag₃Sn₂/CNT）。通过XRD,TEM和XPS对其进行了表征,结果表明,相比Pd/CNT和Pd-Ag（或Pd-Sn）催化剂的纳米颗粒,Pd-Ag-Sn催化剂展现出了更小的平均颗粒尺寸（2.3 nm）。此外,还通过循环伏安（CV）和计时电流法（CA）测试了这些催化剂对甲酸氧化的电活性,在酸碱介质中,Pd-Ag-Sn/CNT对甲酸氧化都表现出了更高的电流密度。其中,Pd₇Ag₂Sn₂/CNT催化剂在酸碱介质中的电流密度分别是108.8和211.3 mA·cm^-2,相应的Pd质量电流密度高达1 364和2 640 mA·mg^-1,远远高于商业Pd/C,表明Pd-Ag-Sn/CNT催化剂对甲酸氧化表现出了极好的电催化活性。     

A novel Prussian blue‐magnetite composite synthesized by self‐template method and its application in reduction of hydrogen peroxide

A novel Prussian blue (PB)‐Fe₃O₄ composite has been prepared for the first time by self‐template method using PB as the precursor. According to this method, Fe₃O₄ nanoparticles distributed uniformly on the surface of PB cube. The feed ratio of sodium acetate to PB has been proved to be a key factor for magnetic properties and electro‐catalysis properties of the composite. Under the experimental conditions, the saturation magnetization value (Ms) of PB‐Fe₃O₄–2 composite was 22 emug^?1, while the Ms value of other samples reduced. The composites also showed a good peroxidase‐like activity for the oxidation of substrate 3,3,5,5‐tetramethylbenzidine (TMB) in the presence of H₂O₂. The catalytic reduction of hydrogen peroxide capacity was PB‐Fe₃O₄–1> PB‐Fe₃O₄–2> PB‐Fe₃O₄–3> PB‐Fe₃O₄–0, which confirmed the Fe(II) centres in PB surface and Fe₃O₄ nanoparticles had synergistic effect on catalytic reduction of hydrogen peroxide.     

Comparison of the properties of waterborne polyurethane/multiwalled carbon nanotube and acid‐treated multiwalled carbon nanotube composites prepared by in situ polymerization

A series of waterborne polyurethane (WBPU)/multiwalled carbon nanotube (CNT) and WBPU/nitric acid treated multiwalled carbon nanotube (A‐CNT) composites were prepared by in situ polymerization in an aqueous medium. The optimum nitric acid treatment time was about 0.5 h. The effects of the CNT and A‐CNT contents on the dynamic mechanical thermal properties, mechanical properties, hardness, electrical conductivity, and antistatic properties of the two kinds of composites were compared. The tensile strength and modulus, the glass‐transition temperatures of the soft and hard segments (T_gs and T_gh, respectively), and ΔT_g (T_gh − T_gs) of WBPU for both composites increased with increasing CNT and A‐CNT contents. However, these properties of the WBPU/A‐CNT composites were higher than those of the WBPU/CNT composites with the same CNT content. The electrical conductivities of the WBPU/CNT1.5 and WBPU/A‐CNT1.5 composites containing 1.5 wt % CNTs (8.0 × 10⁻⁴ and 1.1 × 10⁻³ S/cm) were nearly 8 and 9 orders of magnitude higher than that of WBPU (2.5 × 10⁻¹² S/cm), respectively. The half‐life of the electrostatic charge (τ_1/2) values of the WBPU/CNT0.1 and WBPU/A‐CNT0.1 composites containing 0.1 wt % CNTs were below 10 s, and the composites had good antistatic properties. From these results, A‐CNT was found to be a better reinforcer than CNT. These results suggest that WBPU/A‐CNT composites prepared by in situ polymerization have high potential as new materials for waterborne coatings with good physical, antistatic, and conductive properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3973–3985, 2005     

Catalytic properties of the polyoxometalate [Ti2(OH)2As2W19O67(H2O)]8? in selective oxidations with hydrogen peroxide

The catalytic properties of the sandwich polyoxometalate [Ti₂(OH)₂As₂W₁₉O₆₇(H₂O)]⁸⁻, which contains two (B-α-As^IIIW₉O₃₃) fragments linked together by a “belt” consisting of one octahedral WO(H₂O)⁴⁺ and two square-pyramidal Ti(OH)³⁺ groups, have been investigated in the selective liquid-phase oxidation of organic compounds by aqueous hydrogen peroxide. The polyoxometalate shows high catalytic activity and selectivity in the oxidation of alkenes, alcohols, diols, and thioethers. The composition of the reaction products indicates that hydrogen peroxide is activated via a heterolytic mechanism.     

Synthesis of TiO2/CNT Composites and its Photocatalytic Activity Toward Sudan (I) Degradation

Semiconductor photocatalysis has the potential for achieving sustainable energy generation and degrading organic contaminants. In TiO₂, the addition of carbonaceous nanomaterials has attracted extensive attention as a means to increase its photocatalytic activity. In this study, composites of TiO₂ and carbon nanotubes (CNT) in various proportions were synthesized by the hydrothermal method. The crystalline structures, morphologies, and light absorption properties of the TiO₂/CNT photocatalysts were characterized by PXRD, TEM and UV–Vis absorption spectra. The photocatalytic efficiency of the composites was evaluated by the degradation of Sudan (I) in UV–Vis light. Introducing 0.1–0.5 wt% CNT was shown to substantially improve the photoactivity of TiO₂. The composite with 0.3 wt% CNT showed the best catalytic activity, and its reaction activation energy was calculated as 39.57 kJ mol^?1 from experimental rates. The degradation products of Sudan (I) with different irradiation durations were characterized by Fourier transform infrared spectroscopy, and a degradation reaction process was proposed.     

有序介孔锰氧化物催化过氧化氢降解水中诺氟沙星

采用硬模板法制备了有序介孔氧化锰,并用过氧化氢氧化诺氟沙星的降解率及其抗菌活性变化评价了其催化活性.研究发现,有序介孔锰氧化物表现出较高的催化活性;低pH有利于提高其催化活性.与单独过氧化氢氧化过程相比,有序介孔锰氧化物的存在明显减弱了诺氟沙星的抗菌活性.叔丁醇对催化体系的抑制作用表明有序介孔锰氧化物促进了过氧化氢分解生成羟基自由基.通过对诺氟沙星在催化过程中的分解产物鉴定,提出了可能的分解途径.     

A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3‐Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide

In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3‐aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO‐APTES) and hydrogen peroxide sensor based on rGO‐APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X‐ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO‐APTES/GOx/GC and Nf/rGO‐APTES/GC composites showed good electrocatalytical activity toward glucose and H₂O₂, respectively. The Nf/rGO‐APTES/GC electrode exhibited a linear range of H₂O₂ concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 μA mM⁻¹ cm⁻². The Nf/rGO‐APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 μM and sensitivity of 75.26 μA mM⁻¹ cm⁻². Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.     

Flow Injection Determination of Hydrogen Peroxide Using a Carbon Paste Electrode Modified with a Manganese Dioxide Film

Abstract

A manganese dioxide film modified carbon paste electrode was developed for use as an amperometric sensor for the determination of hydrogen peroxide (H₂O₂) in ammoniacal aqueous solutions. The electrode showed a stable response towards H₂O₂ after electrochemical activation. Effects of flow rate, operating potential, concentration, injection volume and interferences were investigated. A linear response towards H₂O₂ from 5 μg.l^?1 to 450 mg.l^?1 and a detection limit (3 signal-to-noise ratio) of 4.7 μg.l^?1 was found. The method was employed for the determination of H₂O₂ in rain water samples.