Electrocatalytic Oxidation and Determination of Sulfite with a Novel Copper‐Cobalt Hexacyanoferrate Modified Carbon Paste Electrode

The electrocatalytic oxidation of sulfite has been studied at a stable electroactive thin film of copper‐cobalt hexacyanoferrate (CuCoHCF) hybrid electrodeposited on a carbon paste electrode (ECMCPE). A linear range of 5 μM to 5 mM of sulfite, with an experimental detection limit of 1 μM, was obtained using the cyclic voltammetric method. The oxidation of sulfite showed no significant fouling effect on the modified electrode surface at sulfite concentrations below 5 mM. The proposed modified electrode exhibited several attractive features, including simple preparation, fast response, good stability and repeatability, and could be applied to sulfite determination in real samples.     

铁氰化镍化学修饰电极对亚硫酸根离子的电催化氧化及其应用

本文采用电化学方法在玻碳(GC)基体上制备出性能稳定的铁氰化镍(NiHCF)修饰膜电极,表征了NiHCF膜的电化学行为,研究了其对SO_3~(2-)离子的电催化氧化作用。结果表明,SO_3~(2-)离子在NiHCF/GC上氧化是受NiHCF媒介作用的,属EC平行催化反应。催化峰电流与SO_3~(2-)离子浓度在1.0×10~(-6)～2.0×10~(-2)mol/L范围内呈线性关系,检测限可达5.0×10~(-7)mol/L。用于测定空气中SO_2含量,结果良好。     

铁氰化镍化学修饰电报对多巴胺电催化氧化及其测定

本文采用电化学方法在导电基体电极上制备出性能追定的铁氰化锌（ＮｉＨＣＦ）修饰膜电极，对Ｎｉ－ＨＣＦ膜电极的电化学行为进行了表征，并研究了其对神经传导物质，多巴胺（ＤＡ）的电催化氧化作用。结果表明对于在空白玻碳电报（ＧＣ）上氧化电位较高的ＤＡ，ＮｉＨＣＦ在可通过媒介作用促其氧化电位降低约２００ｍＶ，大大提高了其电子转移速率；而且在ＤＡ的浓度为１．０×１０－６—１．０×１０－２ｍｏｌ／Ｌ范围内，催化峰电流与ＤＡ浓度呈良好的线性关系，检测限可达５．０×１０－７ｍｏｌ／Ｌ。用于ＤＡ药物针剂的测定，结果良好。     

Electrocatalytic Reduction of Nitrite by Phosphotungstic Heteropolyanion. Application for Its Simple and Selective Determination

Three couples of reversible redox peaks of the PW₁₂O₄₀^3? (PW₁₂) anion, which are composed of two one‐electron and one two‐electron processes occur in the potential range from +0.25 to ?0.7 V in aqueous solutions. The electrocatalytic reduction of nitrite has been studied by the first redox couple of the PW₁₂ anion at the surface of a carbon paste electrode. Cyclic voltammetric and chronoamperometric techniques were used to investigate the suitability of PW₁₂ anion as a mediator for nitrite electrocatalytic reduction in aqueous solution with strongly acidic concentration of H₂SO₄. Results showed that H₂SO₄ 1.00 M is the best medium for this purpose. In the optimum concentration of H₂SO₄, the electrocatalytic ability about 500 mV can be seen and the homogeneous second‐order rate constant (k_s) for nitrite coupled catalytically to PW₁₂ anion was calculated as 2.52×10³ M^?1 s^?1 using the Nicholson–Shain method. According to our voltammetric experiments, the catalytic reduction peak current was linearly dependent on the nitrite concentration and the linearity range obtained was 3×10^?5 to 1.00×10^?3 M. The detection limit has been found to be 2.82×10^?5 M (2σ). This method has been applied as a selective, simple, and precise method for determination of nitrite in real samples.     

Pt/PAn/Ti电极的制备及对甲醛的电催化氧化

通过循环伏安的电化学方法在金属钛基体上先后进行苯胺的聚合和金属铂的电化学沉积,得到以金属钛为基体的聚苯胺载铂电极(Pt/PAn/Ti),并通过扫描电镜和循环伏安法对该电极进行了表征。通过研究甲醛在该电极上的电催化氧化行为,考察了载铂量对甲醛氧化效果的影响及PAn在电催化氧化甲醛的过程中所起的作用。结果表明,载铂量与甲醛的氧化有一定的关系,PAn的存在使得铂微粒分散程度更好,有效面积更大,与相同铂沉积量的Pt/Ti电极相比,甲醛在其上的正向扫描氧化峰电流密度增加了2.3倍,电位负移了40mV;反向扫描氧化峰电流密度增加了5倍,电位负移了30mV。同时,PAn的存在也增强了电极的抗中毒能力。     

Electrocatalytic Oxidation of Paracetamol on Ni and NiCu Alloy Modified Glassy Carbon Electrode

In this study we investigated the electrocatalytic oxidation of anti‐inflammatory drug (paracetamol) on Nickel and Nickel–copper alloy modified glassy carbon electrodes (GC/Ni and GC/NiCu) in alkaline solution. These electrodes prepared by galvanostatic method and different electrochemical techniques such as cyclic voltammetry and chronoamperometry were used to track the oxidation process and its kinetics. From Voltammetric studies we concluded that in the presence of drugs the anodic peak current of low valences Nickel species increased, followed by a decrease in the corresponding cathodic current peak. This indicates that drugs were oxidized on the redox mediator which was immobilized on the electrode surface via an electrocatalytic mechanism. Using Laviron's equation, the values of α and k_s for the immobilized redox species were determined. The anodic peak currents show linear dependency with the square root of scan rate. This behavior is the characteristic of a diffusion controlled process. Under the CA regime the reaction followed a Cottrellian behavior and the diffusion coefficient of paracetamol was found in agreement with the values obtained from CV measurements.     

镍纳米线电极对乙醇的电催化氧化动力学参数的测定

循环伏安实验表明,以多孔氧化铝膜为模板制备出的镍纳米线电极对乙醇的电化学催化氧化具有很高的催化活性.用强制对流流体动力学的方法求算出乙醇在镍纳米线电极上的电子传递过程的速率常数高于许多文献报导值,而电子传递过程的随后步骤的速率常数相近.     

乙酰二茂铁对亚硫酸盐的电催化氧化及其在锅炉水中亚硫酸盐的测定

用循环伏安法研究了玻碳电极上乙酰二茂铁对亚硫酸盐的电催化氧化行为,试验发现:在中性介质中乙酰二茂铁浓度为6×10-5 mol·L-1时该催化氧化反应的峰电流与亚硫酸盐的浓度在2.0×10-4～2.4×10-3 mol·L-1范围内呈线性关系,回归方程为IPa=4.962×10-3C-0.297,相关系数为0.999 7.将该方法应用于锅炉水中亚硫酸盐的测定,所得结果与碘量法测得的结果相符.测定结果的RSD(n=6)值在0.3%～1.7%之间,回收率试验结果在97.4%～118.2%之间.     

亚硫酸根在化学修饰电极上催化氧化的动力学表征

本文采用Saveant-Andrieux电催化反应动力学理论,表征了SO₃^2-在经Nation-Os(bpy)₃^2+/3+修饰后的玻碳电极上的电催化体系的动力学行为,用动力学区域图确定体系的动力学类型.当反应物浓度从8×10^-5变至1.28×10^-3(mol/L)时,体系始终遵循"SR"的动力学行为。     

Electrocatalytic Oxidation of Methanol on a Nickel‐Porphyrin IX Complex Modified Glassy Carbon Electrode in Alkaline Medium

Electrocatalytic oxidation of methanol on a glassy carbon disc electrode modified with Ni(II)‐hematoporphyrin IX, complex and conditioned by potential recycling in a limited range (between 100 and 600 mV vs. SCE) in 0.10 M NaOH solution, abbreviated as NiOHPME(A), was studied by cyclic voltammetry in alkaline medium. The results were compared with those obtained for a NiO modified glassy carbon electrode, NiOME, prepared in similar conditions. The findings show that the NiOHP film at NiOHPME(A) behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium via Ni(III) species with the cross‐exchange reaction occurring throughout the layer at a low concentration of methanol and for a thin film of modifier. A plausible mechanism was proposed for catalytic oxidation of methanol at NiOHP modified electrode. Moreover, the effects of various parameters such as the scan rate, methanol concentration, thickness of NiOHP film and the real surface area of modified electrode on the oxidation of methanol were investigated. Finally, it has been shown that the NiOHPME(A) has a long‐term stability toward the oxidation of methanol.     

Electrocatalytic Oxidation of Estrogenic Phenolic Compounds at a Nickel‐Modified Glassy Carbon Electrode

This paper demonstrates for the first time, successful electrocatalytic oxidation of electroactive estrogenic phenolic compounds (EPCs) at a nickel‐modified glassy carbon electrode (Ni‐GCE). The electrode was evaluated in terms of electrocatalytic activity, sensitivity, linear dynamic range, limit of detection, and response stability. In comparison to bare glassy carbon electrode, current amplification was observed for EPCs at Ni‐GCE, for example, for a 40 µM estrone at Ni‐GCE was amplified by a factor of 1224. The Ni‐GCE gave good figures of merit with no evidence of electrode fouling. As an example, the limit of detection (S/N=3) for 17β‐estradiol was 100 nM and the response precision (n=5) was 3.4 %.     

Electrocatalytic Determination of Histamine on a Nickel‐Film Glassy Carbon Electrode

The electrocatalysed oxidation of histamine on a thin film nickel electrode was investigated for the purpose of its chronopotentiometric determination. The oxidation mechanism implies complex and combined processes of histamine physical adsorption and consequent oxidation via joined oxidation potency of a constant current and electrochemically generated nickel‐oxihydroxide, which played a role of an electron transfer catalyst. Experimental parameters affecting the oxidation process, including type and concentration of supporting electrolyte, initial potential, oxidation current, temperature and concentration time, were optimised. Using a 240 s accumulation time, limit of detection and quantitation were 0.11 mg L^?1 and 0.29 mg L^?1 of histamine, respectively.     

A New Heated Nickel Oxyhydroxide Covered Nickel Wire Electrode and Its Improved Electrocatalytic Oxidation for Methanol

A new heated nickel oxyhydroxide covered nickel wire electrode (HNONE) was fabricated and AC heating circuit was used to heat the electrode. Furthermore, the improved electrocatalytic activity of the HNONE for methanol oxidation at elevated electrode temperature was demonstrated. A detection limit of 2.1×10^?4 M (S/N=3) could be obtained with an electrode temperature of 80 °C, about one magnitude lower than that at room temperature 20°. And the sensitivity was also enhanced about 10 times.     

Electrocatalytic Oxidation of Sulfite on a Cobalt Pentacyanonitrosylferrate Film Modified Glassy Carbon Electrode

The electrocatalytic oxidation of sulfite has been studied on the cobalt pentacyanonitrosylferrate modified glassy carbon electrode (CoPCNF). The CoPCNF films on the glassy carbon electrodes show an excellent electrocatalytic activity toward the oxidation of sulfite in 0.5 M KNO₃. The kinetics of the catalytic reaction was investigated by using cyclic voltammetry, rotating disk electrode (RDE) voltammetry and chronoamperometry. The average value of the rate constant, K, for the catalytic reaction and the diffusion coefficient, D, were evaluated by different approaches for sulfite and found to be 2.9×10² M^?1s^?1 and 4.6×10^?6 cm²s^?1, respectively. At a fixed potential under hydrodynamic conditions (stirred solutions), the oxidation current is proportional to the sulfite concentration and the calibration plot was linear over the concentration range 5×10^?6–1×10^?4 M. The detection limit of the method is 3×10^?6 M., low enough for the trace sulfite determination.     

石墨烯修饰玻碳电极对多巴胺的电催化氧化

通过3-巯丙基三乙氧基硅烷(METMS)将氧化石墨烯(GO)固载到玻碳电极(GCE)表面, 用电化学方法还原GO制备石墨烯修饰玻碳电极(rGO-METMS-GCE). 利用傅里叶变换红外光谱(FTIR)、 拉曼光谱(Raman)、 扫描电子显微镜(SEM)和原子力显微镜(AFM)等技术对GO和rGO-METMS-GCE的结构和表面形貌进行表征. 采用循环伏安(CV)和差分脉冲溶出伏安(DPV)法研究了rGO-METMS-GCE对多巴胺(DA)的电催化氧化性能及反应机理. 结果表明, 与裸GCE相比, DA在rGO-METMS-GCE电极上的氧化还原峰电流(i_pa和i_pc) 增大4倍, 氧化峰电位负移106 mV, 氧化峰与还原峰电位差(ΔE_p)从202 mV降低至66 mV, DA电化学氧化可逆性明显改善, 表明rGO-METMS-GCE对DA电化学氧化具有显著电催化作用. DA在rGO-METMS-GCE上的反应机理为单电子转移过程.     

铁氰化镍修饰电极对抗坏血酸电催化氧化的研究

抗坏血酸(AH_2)在玻碳和铂电极上的过电位较大,其电极反应不可逆.有关AH_2在碳及其它修饰电极上的电催化氧化已有一些报道,如减压热处理、Al_2O_3微粒研磨、普鲁士蓝修饰膜和聚乙烯二茂铁修饰膜等.本文研究了铁氰化镍修饰膜电极催化AH_2氧化的电化学行为.发现其阳极峰电流与AH_2浓度呈线性关系,可测定1×10~(-7)mol/L的AH_2,其灵敏度比聚乙烯二茂铁修饰电极提高一个数量级.用于蔬菜、水果中AH_2的测定,结果满意.     

Electrochemical Detection of NADH,Cysteine, or Glutathione Using a Caffeic Acid Modified Glassy Carbon Electrode

A modified electrode was prepared using electrodeposition methods to immobilize caffeic acid (CAF) onto the surface of a glassy carbon electrode (GCE) to create a polymer suitable for biosensor development. The polymer film coverage of the surface bound species was further optimized using electrodeposition methods, thus increasing the surface coverage to ca. 10^?9 mol cm^?2. Using cyclic voltammetry, the modified carbon electrode was used to facilitate and observe the electrocatalytic oxidation of coenzymes such as NADH, cysteine, and glutathione at different concentrations. A calibration curve was determined in each case within the concentration range; 300 nM to 10 mM, with the limits of detection (LOD) of 246 µM, 99 µM, 2.2 µM for NADH, cysteine, and glutathione respectively.     

Determination of Glycerol in Biodiesel Using a Nickel(II) Oxyhydroxide Chemically Modified Electrode by Cyclic Voltammetry

A glassy carbon electrode chemically modified with nickel oxyhydroxide from a nickel hexacyanoferrate (NiHCF) film was used to determine glycerol in biodiesel by cyclic voltammetry. The modified electrode exhibited a linear response to glycerol concentration in the range from 0.05 to 0.35 mmol L^?1, and a detection limit of 0.030 mmol L^?1. The glycerol concentration found in the biodiesel sample was 0.156 mmol L^?1. The method developed in this study showed a recovery of (100.3±5.0)%.     

Electrochemical Quartz Crystal Impedance Study of Glucose Oxidation on a Nickel Hydroxide Modified Au Electrode in Alkaline Solution

The electrochemical quartz crystal impedance (EQCI) technique has been applied to investigate glucose oxidation on bare and Ni(OH)₂‐modified Au electrodes in 0.2 mol L^?1 KOH aqueous solution. The EQCI responses suggest different contributions of H⁺‐release and OH^?‐incorporation reactions of the Ni(OH)₂‐film redox process in 0.2 mol L^?1 aqueous KOH at different potentials. Glucose adsorption on the Ni(OH)₂‐modified Au electrode was studied. A mechanism for potential cyclic redox process of glucose at Ni(OH)₂‐modified Au electrode is suggested, mainly based on a comparative EQCI analysis with direct glucose oxidation on bare gold and glucose ad‐/desorption on Ni(OH)₂ film.     

镍氢氧化物修饰玻碳电极的制备及其电化学行为

采用一种新方法———镀膜/循环伏安法成功制备了镍氢氧化物修饰玻碳电极。考察了影响镍氢氧化物膜电催化活性的因素,确定最佳富集时间为2min,最佳富集电位为-1.4V。讨论了成膜过程及机理。膜氧化峰电流及催化氧化峰电流均受扩散控制。制得的镍氢氧化物膜修饰电极具有相当的稳定性,并对H2O2的电氧化表现出较高的电催化活性。该电极对H2O2响应的线性范围为1.71×10-5~1.33×10-2mol/L,检出限为2.86×10-6mol/L(S/N=3)。