H2O2-Zerfall in Gegenwart von Polyeisenphthalocyaninen

The kinetics of the H₂O₂ decomposition in acidic medium and the electrochemical activity of different iron-polyphthalocyanine catalysts for the O₂ reduction in fuel cells were studied. It was found that the reaction order of the H₂O₂ decomposition depends on the initial concentration. For lower concentrations a first order and for the higher ones a second order relationship was found. The change of the reaction order with the increase of H₂O₂ concentration can be explained by a varying cover of the catalyst surface. Catalytic and electrochemical activities of iron-polyphthalocyanine depend on the conditions of the synthesis.

     

Simple Electrodeposition of Dendritic Pd Without Supporting Electrolyte and Its Electrocatalytic Activity Toward Oxygen Reduction and H2O2 Sensing

Metallic palladium (Pd) electrocatalysts for oxygen reduction and hydrogen peroxide (H₂O₂) oxidation/reduction are prepared via electroplating on a gold metal substrate from dilute (5 to 50 mM) aqueous K₂PdCl₄ solution. The best Pd catalyst layer possessing dendritic nanostructures is formed on the Au substrate surface from 50 mM Pd precursor solution (denoted as Pd‐50) without any additional salt, acid or Pd templating chemical species. The Pd‐50 consisted of nanostructured dendrites of polycrystalline Pd metal and micropores within the dendrites which provide high catalyst surface area and further facilitate reactant mass transport to the catalyst surface. The electrocatalytic activity of Pd‐50 proved to be better than that of a commercial Pt (Pt/C) in terms of lower overpotential for the onset and half‐wave potentials and a greater number of electrons (n) transferred. Furthermore, amperometric i–t curves of Pd‐50 for H₂O₂ electrochemical reaction show high sensitivities (822.2 and ?851.9 µA mM^?1 cm^?2) and low detection limits (1.1 and 7.91 µM) based on H₂O₂ oxidation H₂O₂ reduction, respectively, along with a fast response (<1 s).     

Bromide ions induced chaotic behavior in H2O2–H2SO4–Pt electrochemical system

We have found a new chaotic current oscillation in the H₂O₂–H₂SO₄–Pt electrochemical system due to the addition of small amounts of bromide ions. In the system with bromide ions, an oscillation, called oscillation D, appears near the potential where another oscillation, called oscillation A, appears. The chaotic oscillation is observed in a potential region where both oscillations A and D simultaneously appear. When the electrode potential is stepped to a potential in the above region from the rest potential, a period-1 oscillation first appears for a while. A period-doubling bifurcation cascade then occurs, which is followed by a chaos. The appearance of the chaotic oscillations is explained on the basis of the reported mechanisms for oscillations A and D.Dedicated to Professor György Horányi to celebrate his 70th birthday in recognition of many contributions to electrochemistry.     

An Enzyme-free Electrochemical H2O2 Sensor Based on a Nickel Metal-organic Framework Nanosheet Array

In this work, we reported the development of a nickel metal-organic framework nanosheet array on Ti-mesh (Ni-MOF/TM) as an enzyme-free electrochemical sensing platform for H₂O₂ determination. The as-obtained sensor exhibited outstanding detection properties of H₂O₂, which might be gifted from the large specific surface area, abundant active sites of Ni-MOF nanoarrays. The sensor displayed a good linear range (0.8 μM–4.6×10³ μM), a detection limit as low as 0.26 μM, a high sensitivity (307.5 μA mM⁻¹ cm⁻²), and a rapid response. Moreover, this enzyme-free sensor is promising for point-of-care (POC) testing of H₂O₂ in human serum attribute to the excellent performance of Ni-MOF and the simple preparation process of the sensor.     

无溶剂条件下反应控制相转移催化氯丙烯氧化制环氧氯丙烷

系统地研究了无溶剂条件下,H2O2为氧源,反应控制相转移催化剂[(C16H33(70%)+C18H37(30%))N(CH3)3]3[PW4O16]催化氯丙烯环氧化制环氧氯丙烷反应.结果表明,在氯丙烯/H2O2/催化剂(摩尔比)=400∶100∶1条件下,50～55℃反应3 h,环氧氯丙烷的收率为85～87%.在NaH2PO4存在下,催化剂循环使用5次,活性无明显降低,新鲜催化剂和回收催化剂的31P MAS NMR谱分析结果表明NaH2PO4对催化剂结构和组成具有稳定作用.     

Vc-Functionalized Fe3O4 Nanocomposites as Peroxidase-like Mimetics for H2O2 and Glucose Sensing

A simple and efficient colorimetric biosensing for hydrogen peroxide and glucose with peroxidase-like vitamin C(V_c) functionalized Fe₃O₄ magnetic nanoparticles(V_c/Fe₃O₄MNPs) as a catalyst is reported. Compared with Fe₃O₄ MNPs and other catalysts, V_c/Fe₃O₄ MNPs exhibited superior catalytic properties. Kinetic studies indicated that vitamin C incorporated on Fe₃O₄ MNPs improved the affinity toward H₂O₂. As low as 0.29 μmol/L H₂O₂ can be detected with a wide linear range of 0.5—100 μmol/L H₂O₂; moreover, as low as 0.288 μmol/L glucose can be detected with a linear range of 0.5—25 μmol/L glucose. The detection method was highly sensitive in sensing H₂O₂ and glucose. The robustness of V_c/Fe₃O₄ MNPs rendered them suitable for wide ranging applications.     

Amperometric Detection of H2O2 Using Gold Electrodes Modified with Starburst PAMAM Dendrimers and Prussian Blue

Gold‐bead electrodes were modified by covalent bonding or physical adsorption of several Starburst PAMAM dendrimers (generations 2.0, 3.0 and 4.0) followed by absorption of Prussian Blue (PB). The covalent dendrimer‐PB‐modified electrodes can be used as amperometric sensors of H₂O₂ in aqueous solution. They offer enhanced sensitivity with correspondingly lower detection and quantification limits compared to similar amperometric detectors.     

Hemin-phytic Acid Functionalized Porous Conducting Polymer Hydrogel With Good Biocompatibility for Electrochemical Detection of H2O2 Released From Living Cells

A novel hemin/phytic acid doped polyaniline (PA-PANI) hydrogel composite was prepared through a simple chemical and self-assembly method, which was modified onto electrode for electrochemical detection of H₂O₂ released from living cells. It showed good analytical performance with high sensitivity, selectivity and a rapid response for the analysis of H₂O₂ in the range of 2 to 102 μM, with the detection limit of 1.2 μM. The favorable results mainly originated from both the high conductivity of PA-PANI hydrogel and its network structure preventing hemin from self-dimerization to provide active catalytic species. Furthermore, PA-PANI with good biocompatibility allowed living cells to adhere and resulted in a short diffusion distance between H₂O₂ released from cells and electrode.     

Deep Oxidative Desulfurization of Thiophenic Model Oil/Natural Gas Condensate Over Tungsten/Molybdenum Oxides Using H2O2 as Oxidant

Supported Na₂WO₄/ZSM5 as catalyst was used for deep oxidative desulfurization (ODS) of mixed thiophenic compounds model oil and natural gas condensate under mild conditions by using hydrogen peroxide as oxidant. A one factor at a time optimization strategy was applied for optimizing the parameters such as temperature, loading of catalysts, reaction time, type of extractant and oxidant to S‐compounds molar ratio. The corresponding products can be easily removed from the model by using MeCN as best extractant. Results showed highly catalytic activity of Na₂WO₄/ZSM5 for the oxidative removal of dibenzothiophene and mixed thiophenic model oil under atmospheric pressure at 75 °C in a biphasic system. By applying the ODS to mixed model/MeCN and gas condensate/MeCN, the conversion reached to 94 and 81 %, respectively, using 40 % loading Na₂WO₄/ZSM5 as catalysis under the optimal conditions. To investigate the oxidation and adsorption effects of gas condensate composition on ODS, effects of cyclohexene, 1,7‐octadiene, and o‐xylene were studied with different concentrations.     

Layer-by-layer assembled multilayer of graphene/Prussian blue toward simultaneous electrochemical and SPR detection of H2O2

A new type of chemically converted graphene sheets, cationic polyelectrolyte-functionalized ionic liquid decorated graphene sheets (PFIL-GS) composite, was synthesized and characterized by Ultraviolet-visible (UV-vis) absorption, Fourier transform infrared, and Raman spectroscopy. It was found that the presence of PFIL enabled the formation of a very stable aqueous dispersion due to the electrostatic repulsion between PFIL modified graphene sheets. With respect to the excellent dispersibility of this material, we have fabricated a novel PFIL-GS/Prussian blue (PB) nanocomposite multilayer film via classic layer-by-layer (LBL) assembly. The assembly process was confirmed by UV-vis spectroscopy and surface plasmon resonance (SPR) spectroscopy, which showed linear responses to the numbers of the deposited PFIL-GS/PB bilayers. Moreover, the as-prepared composite films were used to detect hydrogen peroxide (H₂O₂) by electrochemical surface plasmon resonance (EC-SPR) spectroscopy. This real time EC-SPR technique can provide simultaneous monitoring of both optical SPR signal and electrochemical current responses upon injecting H₂O₂ into the reaction cell. The experimental results revealed that both the electrochemical and SPR signal exhibited splendid linear relationship to the concentration of the injected H₂O₂, and the detection limit could be up to 1 μM.     

甲烷氧等离子体直接合成过氧化氢

本文利用介质阻挡放电(DBD)方法, 在室温和常压下将甲烷和氧气的混合气体进行等离子体活化, 通过甲烷和氧等离子体直接气相反应高收率合成H2O2. 该方法能有效克服氢氧直接法合成H2O2受到原料气配比严格限制的缺点.     

Molybdenum Carbide as Alternative Catalysts to Precious Metals for Highly Selective Reduction of CO2 to CO

Rising atmospheric CO₂ is expected to have negative effects on the global environment from its role in climate change and ocean acidification. Utilizing CO₂ as a feedstock to make valuable chemicals is potentially more desirable than sequestration. A substantial reduction of CO₂ levels requires a large‐scale CO₂ catalytic conversion process, which in turn requires the discovery of low‐cost catalysts. Results from the current study demonstrate the feasibility of using the non‐precious metal material molybdenum carbide (Mo₂C) as an active and selective catalyst for CO₂ conversion by H₂.     

Au‐TiO2/Graphene Nanocomposite Film for Electrochemical Sensing of Hydrogen Peroxide and NADH

We describe a simple method for preparing Au‐TiO₂/graphene (GR) nanocomposite by deposition of Au nanoparticles (NPs) on TiO₂/GR substrates. The as‐prepared Au‐TiO₂/GR was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The presence of Au NPs on TiO₂/GR surface remarkably improves the electrocatalytic activity towards the oxidation of hydrogen peroxide (H₂O₂) and β‐nicotinamide adenine dinucleotide (NADH). The Au‐TiO₂/GR modified glassy carbon (GC) electrode exhibits good amperometric response to H₂O₂ and NADH, with linear range from 10 to 200 µM and 10 to 240 µM, and detection limit of 0.7 and 0.2 µM, respectively.     

石墨烯-聚多巴胺纳米复合材料制备过氧化氢生物传感器

通过合成具有仿生功能的石墨烯-聚多巴胺纳米材料,将其与辣根过氧化酶组装到电极表面,以对苯二酚为电子媒介体制备H2O2传感器.此修饰电极对H2O2具有良好的电催化活性,检测的线性范围为5.0×10-7～3.3×10-4 mol/L;线性回归方程为Y=29.69x+ 0.04577,相关系数为R=0.9995;检出限为3.7×10-7 mol/L(S/N=3).     

Synthesis and Crystal Structure of [C10N2H10]2[P2Mo5O21(OH)2]·2H2O

The crystal structure of [C₁₀N₂H₁₀]₂[P₂Mo₅O₂₁(OH)₂] · 2H₂O, contains the heteropolyanion, [P₂Mo₅O₂₁(OH)₂]^4—, together with diprotonated 4, 4′‐bipyridine. The heteropolyanion is built up from five MoO₆ octahedra sharing four common edges and one common corner, capped by two PO₃(OH) tetrahedra. The structure is stabilized by hydrogen bonds involving the hydrogen atoms of the 4, 4′‐bipyridine, water molecules and the oxygen atoms of the pentamolybdatobisphosphate. This is the first example that this kind of cluster could be isolated in the presence of a poly‐functional aromatic molecule ion. Crystal data: triclinic, P1¯ (No. 2), a = 9.983(2)Å, b = 11.269(2)Å, c = 17.604(4)Å, α = 73.50(3)°, β = 84.07(3)°, γ = 67.96(3)°; V = 1760.0(6)ų; Z = 2; R₁ = 0.037 and wR₂ = 0.081, for 9138 reflections [I > 2σ(I)].     

NiCo2O4 纳米线对H2O2电还原的催化性能

以无模板生长法制备了泡沫镍载NiCo2O4纳米线正极材料, XRD和SEM表征结果表明, 所得材料为NiCo2O4纳米线, 以循环伏安法和计时电流法研究了泡沫镍载NiCo2O4纳米线对H2O2电还原的催化性能. 结果显示, 在0.4 mol/L H2O2 和 3.0 mol/L NaOH 溶液中, 当电压为-0.4 V(vs. Ag/AgCl)时, 循环伏安的电流密度达到125 mA/cm2; 当电压为-0.2, -0.3和 -0.4 V 时, 在30 min 的测试时间内, 计时电流密度几乎均为一常数, 表明以泡沫镍载NiCo2O4纳米线为催化剂电还原H2O2具有很高的活性和很好的稳定性.     

Synthesis of Functionalized MWCNTs Decorated with Copper Nanoparticles and Its Application as a Sensitive Sensor for Amperometric Detection of H2O2

Functionalized‐multiwall carbon nanotubes decorated with redox active copper nanoparticles have been fabricated for sensitive enzyme‐less H₂O₂ detection. The new nanocomposite was characterized by Transmission electron microscopy, energy dispersive X‐ray analysis and cyclic voltammetry. The response of the modified electrode to H₂O₂ was examined using amperometry at ?0.45 V vs. Ag/AgCl in a buffer solution at pH 10.0. The developed sensor displayed linear concentration ranges of 0.5–10.0 and 10.0–10000.0 µmol L^?1 with a detection limit of 0.3 µmol L^?1. The proposed sensor displayed good selectivity for H₂O₂ detection in the presence of common interferences such as ascorbic acid.     

Polyoxometalate catalysts: toward the development of green H2O2-based epoxidation systems

This paper describes the development of green, efficient H(2)O(2)-based epoxidation systems with three kinds of polyoxometalates: (i) a dinuclear peroxotungstate [W(2)O(3)(O(2))(4)(H(2)O)(2)](2-) (I), (ii) a divacant lacunary polyoxotungstate [gamma-SiW(10)O(34)(H(2)O)(2)]4 (II), (iii) and a divanadium-substituted polyoxotungstate [gamma-1,2-H(2)SiV(2)W(10)O(40)](4-) (III). The highly chemo-, regio-, and diastereoselective epoxidation of various allylic alcohols with only 1 equiv H(2)O(2) in water can be efficiently catalyzed by potassium salt of I (K-I). The catalyst K-I can be recycled with the retention of the catalytic performance. Protonation of a divacant lacunary polyoxotungstate [gamma-SiW(10)O(36)](8-) gives [gamma-SiW(10)O(34)(H(2)O)(2)](4-) (II) with two aquo ligands. The tetra-n-butylammonium salt of II (TBA-II) catalyzes epoxidation of common olefins including propylene with >or=99% selectivity to epoxide and >or=99% efficiency of H(2)O(2) utilization. The bis(mu-hydroxo)bridged dioxovanadium site in [gamma-1,2-H(2)SiV(2)W(10)O(40)](4-) (III) can also efficiently catalyze epoxidation of a variety of olefins with 1 equiv H(2)O(2). Notably, the system with III shows unique stereospecificity, diastereoselectivity, and regioselectivity for the epoxidation of cis/trans olefins, 3-substituted cyclohexenes, and nonconjugated dienes, respectively, which are quite different from those reported for epoxidation systems up to now. Furthermore, the heterogenization of the mentioned polyoxometalates can be achieved by using ionic liquid-modified SiO(2) as a support without loss of catalytic performance.     

An Enzyme‐free H2O2 Sensor Based on Poly(2‐Aminophenylbenzimidazole)/Gold Nanoparticles Coated Pencil Graphite Electrode

A poly(2‐aminophenylbenzimidazole)/gold nanoparticles (P2AB/AuNPs) coated disposable pencil graphite electrode (PGE) was fabricated as an enzyme‐free sensor for the H₂O₂ determination. P2AB/AuNPs and P2AB were successfully synthesized electrochemically on PGE in acetonitrile for the first time. The coatings were characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, Energy‐dispersive X‐ray spectroscopy, Surface‐enhanced Raman spectroscopy, and UV‐Vis spectroscopy. AuNPs interacted with P2AB as carrier enhances the electrocatalytic activity towards reduction of H₂O₂. The analytical performance was evaluated in a 100 mM phosphate buffer solution at pH 6.5 by amperometry. The steady state current vs. H₂O₂ concentration is linear in the range of 0.06 to 100 mM (R²=0.992) with a limit of detection 3.67×10^?5 M at ?0.8 V vs. SCE and no interference is caused by ascorbic acid, dopamine, uric acid, and glucose. The examination for the sensitive determination of H₂O₂ was conducted in commercially available hair oxidant solution. The results demonstrate that P2AB/AuNPs/PGE has potential applications as a sensing material for quantitative determination of H₂O₂.     

Direct Synthesis of H2O2 by a H2/O2 Fuel Cell

Direct synthesis of H₂O₂ solutions by a fuel cell method was reviewed. The fuel cell reactor of [O₂, gas-diffusion cathode electrolyte solutions Nafion membrane electrolyte solutions gas-diffusion anode, H₂] is very effective for formation of H₂O₂. The three-phase boundary (O₂(g)–electrode(s)–electrolyte(l)) in the gas-diffusion cathode is essential for efficient formation of H₂O₂. Fast diffusion processes of O₂ to the active surface and of H₂O₂ to the bulk electrolyte solutions are essential for H₂O₂ accumulation. The maxima H₂O₂ concentrations of 1.2 M (3.5 wt%) and 2.4 M (7.0 wt%) were accomplished by the heat-treated Mn-OEP/AC electrocatalyst with H₂SO₄ electrolyte and by the VGCF electrocatalyst with NaOH electrolyte, respectively, under short circuit conditions.