氢氧根离子在TiO2薄膜电极上的吸附行为和光氧化动力学

在醇的水溶液中，应用电化学方法研究了OH－在TiO2薄膜电极上的吸附行为和光氧化动力学.实验结果表明，OH－在TiO2表面的吸附模型符合Langmuir等温吸附方程式，其光氧化动力学行为能用Langmuir-Hinshelwood动力学方程来描述.在光强足够大时，光电流和OH－在TiO2表面的吸附浓度成正比，这表明，光生空穴仅氧化吸附于TiO2表面的OH－，同时吸附的水分子则不能被氧化.在醇浓度足够高的溶液中，自由基OH•和电子之间的复合反应几乎不发生，这时整个光氧化反应的速控步骤是光生自由基OH•的生成.     

次亚磷酸根离子在铂电极上氧化的机理研究(英文)

用SNIFTIRS和循环伏安法研究次亚磷酸根离子在多晶铂电极上的电氧化机理 .分析了0 .5mol/LH2 SO4 + 0 .1mol/LNaH2 PO2 溶液中原位红外反射谱图与Pt电极电位的关系 ,发现次亚磷酸根离子在Pt上发生解离吸附 ,其氧化产物是H3 PO4 ,不同于在Ni上的氧化产物H2 PO- 3 ,据此提出了酸性溶液中次亚磷酸根离子在Pt上氧化机理的新看法     

磷钼钨杂多酸-L-半胱氨酸自组装膜电极的电化学性质

磷钼钨杂多阴离子通过分子间静电作用吸附在L-半胱氨酸自组装单分子膜修饰金电极表面,制备了磷钼钨杂多酸-L-半胱氨酸自组装超分子膜电极,探讨了成膜条件.采用循环伏安(CV)、计时库仑(CC)、水平衰减全反射傅立叶变换红外光谱(ATR-FTIR)表征了膜的组成及电化学性质.实验发现,该膜电极在1.0 mol•L－1H2SO4溶液中,于0.8～－0.2 V(υs SCE)间CV扫描出现3对稳定、可逆的氧化还原峰,计时库仑法计算了薄膜内的电子传递系数D为 2.64×10－7 cm2•s－1,初步探讨了膜电极的氧化还原性能.     

Pt(111)单晶电极上乙二醇解离吸附反应动力学

运用电化学循环伏安和程序电位阶跃方法研究了乙二醇在Pt(111)单晶电极上的解离吸附过程.动力学研究的定量结果指出,乙二醇解离吸附反应的平均速率随电极电位变化呈火山型分布,其最大值在0.10 V(vs SCE)附近.测得在含2×10－3 mol•L－1乙二醇的溶液中,最大初始解离速率vi为4.35×10－12 mol•cm-－2•s－1.     

次磷酸盐氧化反应历程的研究

对次磷酸盐体系循环伏安曲线－０．４Ｖ（ＳＣＥ）处氧化峰（Ⅱ峰）的特性及本质进行深入研究。结果表明，Ⅱ峰与Ｉ峰直接相关，对应于活性吸附态的偏亚磷酸根氧化生成磷酸根的电极过程，Ⅱ峰是偏亚磷酸根脱出的Ｈａｄｓ＾－离子在电极上发生氧化的结果。确定了吸附态偏亚磷酸根转变为惰性亚磷酸根反应的控速步骤为偏亚磷酸的脱附过程，并估算了脱附速度常数。最后给出可能的吸附态偏磷酸根氧化生成磷酸根的电极历程及总的次磷酸根氧     

聚阿魏酸修饰电极的电化学特性及电催化性能

研究了阿魏酸在玻碳电极表面电聚合成膜的方法和条件,测量了应用电化学方法制备不同厚度的阿魏酸修饰电极的循环伏安行为及其它电化学性质.对厚度为0.5 μm的阿魏酸膜,测得的电子转移系数为0.49,表观电极反应速率常数(ks)为6.56 s－1.扩散系数DR为7.9×108 cm2•s－1,Do为4.48×108 cm2•s－1.该修饰电极对烟酰胺腺嘌呤二核苷酸（NADH）氧化具有很好的催化作用.NADH浓度在0.01～5.0 mmol•dm－3范围内与峰电流呈现良好的线性关系.     

瞬态吸收光谱研究苯与H2O2水溶液的反应机理

利用瞬态吸收光谱技术研究了不同条件下苯与H2O2水溶液复相体系的激光闪光光解情况,考察了其瞬态物种的生长和衰减等行为.研究表明, •OH自由基和苯反应生成C6H6-OH加合物,其反应速率常数在近中性和酸性条件下分别为(8.0～8.1)×109 L•mol－1•s－1和7.7×109 L•mol－1•s－1, 而在碱性时则为(6.7～6.9)×109 L•mol－1•s－1,在有氧条件下C6H6-OH加合物被氧化为C6H6-OHO2后,进一步分解成对苯醌;C6H6-OH加合物和激发态的苯也可直接与H2O2反应生成对苯醌,三种反应途径同时存在.     

C2H3＋NO2反应速率常数的研究

利用激光光解C2H3Br产生C2H3自由基,在气相298 K, 总压2.66×103 Pa的条件下,研究C2H3与NO2的反应,用激光光解-激光诱导荧光（LP-LIF）检测中间产物OH自由基的相对浓度随着反应时间的变化关系,报导了双分子反应C2H3＋NO2的速率常数k(C2H3＋NO2)=(1.8±0.05)×10－11cm3•molec.－1•s－1,同时也得到OH＋NO2反应的速率常数k(OH＋NO2)=(2.1±0.15)×10－12 cm3•molec.－1•s－1.     

酸性溶液中NaH2PO2在铂电极上氧化的原位红外光谱研究

用SNIFTIRS和循环伏安法研究酸性溶液中次亚磷酸钠在多晶铂电极上的电氧化机理.分析了0.5mol/LH2SO4+0.1mol/LNaH2PO2溶液中原位红外反射谱图与电极电位的关系,发现在发生反应的电位下Pt电极上的吸附物种有氢原子和H2PO2,最终的氧化产物是H3PO4而不是H2PO3-,据此提出了酸性介质中次亚磷酸根离子在Pt上氧化的新机理.     

甲醇在Pt表面电化学氧化过程中的化学振荡

基于甲醇电化学氧化的双途径机理,建立了能够表征甲醇电化学氧化过程电位振荡的非线性动力学模型.所建甲醇氧化系统动力学演化模型涉及三个主要的变量:电极电位(e),毒性中间体CO的表面覆盖度(x),含氧物种H2Oa的表面覆盖度(y).通过反应速率常数ki=exp(ai(e-ei))实现了化学反应与电极电位的耦合.研究发现,在不同的电流密度范围内甲醇电化学氧化呈现不同的动力学特征.甲醇电化学氧化时出现的电位振荡现象可以归因为:一是氧化过程中生成了毒性中间体CO,这是产生电化学振荡的诱因;二是强烈依赖于电极电位的非电化学反应,即,含氧物种H2Oa在Pt表面的生成与消失,则是维系振荡的直接原因.而甲醇电化学氧化体系复杂的动力学行为根源在于电极电位e对CO和含氧物种H2Oa所参与反应的耦合反馈作用.对所建模型的数值分析成功地解释了为什么甲醇电化学氧化时出现的电位振荡现象只发生在一定的电流密度范围.     

Anodic and cathodic process of hypophosphite on a Ni-Ag electrode

The reduction and the oxidation of hypophosphite on a Ni-Ag electrode have been studied to provide the information about the phosphorus incorporation mechanisms during the electro-less deposition and the electrodeposition of Ni-P alloys.In the electrooxidation process,an absorbency band around 240nm,which was ascribed to the formation of an intermediate PHO2-,was observed by in situ UV-Vis subtractive reflectance spectroscopy.Accordingly,the electrooxidation of hypophosphite might undergo an H abstraction of hypophosphite from the P-H bond to form the phosphorus-centred radical ' PHO2- ,which was subsequently electrooxidized to the final product,phosphite.In the reduction process Ni-phos-phine compound Ni-(PH3)n was observed by in situ surface Raman spectroscopy.The results from the Raman experiments show that,in the NiSO4-free solution,hypophosphite was reduced only to Ni-phosphine compound,while in the case where NiSO4 coexisted in the solutions,the Ni-phosphine compound,as an intermediate,was oxidise     

Electrocatalytic Oxidation of Hypophosphite on Nickel Electrode ──In Situ UV-Vis Spectroscopic study

ThefactthathypophosphiteisoneofthemostwidelyusedreducingagentsintheNielectrolessdepositionhasstimulatedthestudyofanodicoxidationofhypophosphiteonnicked-ic.Thisanodicreaction,whichisimportantfortheunderstandingoftheNielectrolessdepositionmechanism,isexpectedtobeoneoftheimportantreactionsintheNi-electrolessprocess.Recently,theroleandoxidationmechanismofhypophosphiteinelectrolessdepositionofNi-Palloyhavebeenstudiedindetailusingtheprobebeamdeflection',electrochemistryandinsituIR',lo.However,som…     

Voltammetric and flow-injection determination of carbohydrates using composite electrodes based on carbon nanotubes and Nickel(II) hexacyanoferrate

The catalytic activities of oxo and hydroxo forms of nickel(II) on the surface of a nickel deposit and an inorganic film of nickel(II) hexacyanoferrate(III) (NiHCF) electrodeposited on a glassy-carbon electrode both unmodified and modified by multi-wall or single-wall (also functionalized) carbon nanotubes in the electrooxidation of glucose, sucrose, and maltose are compared. A more pronounced catalytic effect was obtained in the electrooxidation of these carbohydrates on an electrode modified with functionalized singlewall carbon nanotubes and a NiHCF film. Methods are proposed for the voltammetric and flow-injection determination of carbohydrates on this composite electrode. A linear dependence of the analytical signal on the analyte concentration was observed in the range from 5 × 10^?7 to 5 × 10^?2 M under stationary conditions and from 0.003 to 0.3 μmol under flow conditions.     

乳酸在Ni-PTFE复合电极上的电氧化

乳酸在Ni-PTFE复合电极上的电氧化;丙酮酸;疏水性     

Ni-B非晶态合金纳米粉末微电极上甲醇的电催化氧化

应用循环伏安法研究了碱性介质中Ni-B非晶态合金纳米粉末微电极上甲醇的电催化氧化.结果表明,Ni-B非晶态合金纳米粉末微电极表现出很高的甲醇氧化电催化活性,较之高择优取向(220)的镍电极,其氧化起始电位负移了0.04V;氧化电流密度约大2个数量级,根据稳态极化曲线测定,与高择优取向(220)镍电极相比较,在Ni-B非晶态合金纳米粉末微电极上,Ni(Ⅲ)与甲醇反应和Ni(Ⅱ)氧化为Ni(Ⅲ)及其逆反应的速率常数依次约大2个、3个和3个数量级.     

以次磷酸钠为还原剂化学镀铜的电化学研究

通过电化学方法研究了以次磷酸钠为还原剂, 柠檬酸钠为络合剂的化学镀铜体系. 应用线性扫描伏安法, 检测了温度、pH值、镍离子含量对次磷酸钠阳极氧化和铜离子阴极还原的影响. 结果表明, 升高温度能够加速阳极氧化与阴极还原过程; pH值的提高可促进次磷酸钠氧化, 但抑制铜离子还原; 镍离子的存在不仅对次磷酸钠的氧化有强烈的催化作用, 而且与铜共沉积形成合金. 该合金有催化活性, 使化学镀铜反应得以持续进行.     

酸性化学镀镍中次亚磷酸钠阳极氧化行为的研究

采用线性电位扫描和交流阻抗法研究了酸性化学镀镍过程中还原剂次亚磷酸钠的阳极氧化行为。结果表明，次亚磷酸钠的氧化是一个复杂的电化学过程，其阳极氧化行为受本身浓度、溶液温度、阳极扫描速度以及Ｎｉ＾２＋的影响，在其氧化反应之前可能存在异相界面转化步骤，该步骤成为整个氧化过程的控制步骤。     

Electrooxidation of dihydroxybenzenes at a mechanically renewed nickel electrode

The dependence of the potentials and peak currents of the electrooxidation of isomeric dihydroxybenzenes on the polarization mode of a mechanically renewed nickel electrode is studied by direct-current cyclic voltammetry. The results indicate that the oxidation peaks of hydroquinone, pyrocatechol, and resorcinol appear in alkaline (0.05–0.10 M KOH), neutral (0.02–0.10 M Na₂SO₄) and acidic (0.02–0.05 M H₂SO₄) supporting electrolytes. The peak shape and parameters depend on the composition of the supporting electrolyte, which creates the conditions for the formation of different nickel oxides on the electrode surface then involved in the electrooxidation of dihydroxybenzenes. The regeneration of the electrode surface also affects the peak parameters, especially for resorcinol, whose signals completely disappear without the electrode renewal. The analytical signals for three isomeric dihydroxybenzenes are peaks in an alkaline solution, and also hydroquinone and pyrocatechol peaks in neutral and acidic solutions.     

Voltammetric determination of paracetamol at NiO nanoparticles-modified carbon paste electrode in bulk and tablet dosage forms

Nickel oxide (NiO) nanoparticles were synthesized by a rapid method and well characterized. The nanoparticles were then used with graphite powder to prepare modified carbon paste electrode (CPE/NiO) for electrocatalytic oxidation of paracetamol (AC). The CPE/NiO showed higher electrocatalytic activity than nickel rod electrode in electrocatalytic oxidation of AC in alkaline media. The assay of AC, mechanism and kinetics of the electrooxidation process were investigated by cyclic voltammetry and chronoamperometry. The catalytic rate constant and the charge transfer coefficient of AC electrooxidation by the active nickel species and the diffusion coefficient of AC were also reported. The linear dependence of the peak current on the concentration of the AC was observed in the range 2–14 mM. This procedure was successfully applied to the determination of AC in tablets. The results showed sufficient precision, accuracy and achieved a mean recovery of 97.2% (RSD = 6.7%).     

Fabrication of a high sensitive glycine electrochemical sensor based on immobilization of nanostructured Ni chelidamic acid and bimetallic Au-Pt inorganic-organic hybrid nanocomposite onto glassy carbon modified electrode

In this research a novel nickel complex was used as electrocatalyst for electrooxidation of glycine. A nano-structured nickel chelidamic acid was electrodeposited on a bimetallic Au-Pt inorganic-organic hybrid nanocomposite modified electrode. The electrode possesses a three-dimensional (3D) porous network nanoarchitecture, in which the bimetallic Au-Pt NPs serving as metal nanoparticle based microelectrode ensembles are distributed in the matrix of interlaced 3,3′,5,5′-tetramethylbenzidine (TMB) organic nanofibers (NFs). Electrocatalytic oxidation of glycine on the surface of modified electrode was investigated with cyclic voltammetry method and the results showed that the nickel chelidamic acid films displayed excellent electrochemical catalytic activities towards glycine oxidation. The hydrodynamic amperometry at rotating modified electrode at constant potential versus reference electrode was used for detection of glycine. Under optimized conditions the calibration plots are linear in the concentration range 1 μM-0.75 mM and detection limit was found to be 0.3 μM.