掺硼浓度对金刚石薄膜电极电化学性能影响的研究

以不同掺硼浓度的金刚石薄膜作为电极材料,采用循环伏安法和交流阻抗法研究了电极的电化学性能,着重分析了掺硼浓度对金刚石电极电化学性能的影响.结果表明,随着掺硼浓度的增加,电极的电势窗口略微变小,背景电流也随之变大.在铁氰化钾电解液中,未掺杂金刚石薄膜的电极表面进行的不是可逆反应,而硼掺杂金刚石膜电极表面在反应过程中有着良好的活性和准可逆性;并且随着掺硼浓度的增加,其动力学过程主要受扩散过程控制.金刚石膜电极对苯酚模拟有机污染物的循环伏安实验表明,所考察的三个硼浓度不断增加的电极的氧化峰电流密度分别为0.8,1.9和5.1 mA(cm(2,说明在本实验范围内,金刚石膜电极对苯酚催化氧化作用随着掺硼浓度的增加而增强.     

硼氢化钠合成新工艺研究

偏硼酸钠是硼氢化钠的还原副产物。以偏硼酸钠为原料,与金属钠、石英砂进行加氢反应来制备硼氢化钠。用异丙胺对产物进行萃取提纯,制得了纯度较高、收率为47·8%的硼氢化钠产品。萃取剂回收利用率可达85%。     

Pd-Ag/C在硼氢化钠电氧化反应中的电化学行为

采用化学还原法制备了不同原子比的Pd-Ag/C催化剂。通过X射线衍射（XRD）表征了催化剂的晶体结构,并运用循环伏安、计时电流等电化学方法研究了其对硼氢化钠电氧化反应的催化活性。结果表明：适量Ag的掺杂不仅可以提高催化剂的催化活性,而且使得硼氢化钠电氧化反应过程中的转移电子数增加,其中Pd₇₅Ag₂₅/C的催化活性和转移电子数均为最高。     

菁染料单分子膜覆盖的铂电极的电化学特性

L-B膜作为一种单分子膜技术已经得到了广泛的应用。最近很多人用电化学方法研究覆盖有L-B膜电极的特性。许多工作证明了脂肪酸L-B膜具有很强的抑制离子透过和抑制电子隧道电流的能力。而不具备这种性能的L-B膜,则被归之于膜中含有大量针孔所致。Kuhn曾在脂肪酸L-B膜中引入带有共轭双键的偶氮化合物。Zaba     

氢化偶联反应—用硼氢化钠阳极氧化法使乙炔衍生物电化学偶联

氢化偶联反应,是使两个单独苯环化合物偶联成为氢化偶联产物。这类反应是合成染料的重要反应,它对电化学法合成染料有一定的借鉴作用。文献报道用 NaBH_4在苯基衍生物的存在下电解(1a-f),产生不寻常的尾尾相接(tail-to-tail)氢化偶联反应,得到占优势的产物1,4-二苯丁烷衍生物(2a-f),收率为64%—20%。具体步骤:反应在含有 NaI 的二乙醇二甲醚和NaBH_4两者作支持电解质下与反应物(1a-f)一起,在无隔膜电解槽中,以铂片作阳极和阴极,在室温和     

甲醇在碳载纳米Pt电极上的电化学研究

应用循环伏安法制备了nano-Pt/GC修饰电极,优化了铂微粒在电极表面的沉积条件,并用扫描电子显微镜(SEM)和在硫酸中的循环伏安曲线对其进行了表征。结果表明铂微粒较为均匀地分散在玻碳电极表面,粒径约为140nm,电极具有很大的比表面积。循环伏安实验结果表明nano-Pt/GC电极对甲醇电氧化的催化活性明显高于铂片电极,在该修饰电极上甲醇正向扫描和反向扫描时的氧化峰电位分别是0.67V和0.49V,峰电流为61.00mA/cm2和50.50mA/cm2,分别是铂片电极上的3.13倍和3.10倍,有效地提高了金属铂的利用率,铂微粒在电极表面的最佳沉积条件是循环次数为100次和沉积速度为5mV/s。     

在铂电极上循环伏安法氧化二甘醇研究

用循环伏安法研究了含二甘醇的１．０ｍｏｌ·Ｌ＾－１Ｈ２ＳＯ４溶液在铂电极上的电氧化行为,证明它是一个不可逆的复杂的氧化还原过程,并考察了温度和浓度对该过程的影响。     

甲醇在聚苯胺载铂电极上的电催化氧化

用循环伏安法在玻碳电极上电聚合导电高分子聚苯胺用于附载Pt,提高了Pt的分散度。发现甲醇在Pt／PAN／GC电极和Pt／GC电极上均能自发解离出强吸附中间体CO,证实聚苯胺膜的存在有利于提高电极对甲醇的电催化氧化活性,CO在Pt／PAN／GC电极上的氧化峰电流明显高于Pt／GC电极。通过比较甲醇的电催化氧化活性可知,Pt/PAN／GC电极催化氧化甲醇的峰电流为58．68mA/cm^2和50．00mA／cm^2,是Pt／GC电极氧化峰电流的1．6倍和1．7倍。     

丁香酚在活化玻碳电极上的电化学行为

用循环伏安法和差分脉冲溶出伏安法研究了丁香酚在活化玻碳电极于醋酸-醋酸钠（pH=6．0）缓冲溶液中的电化学行为。结果表明,丁香酚在该电极上于0．188V、0．485V有一对氧化还原峰,表明该电极对丁香酚有催化作用。在pH=6．0的醋酸-醋酸钠缓冲液中,用差分脉冲溶出伏安法在该电极上测定了丁香酚,线性范围为4．00×10^-6-2．58×10^-4mol／L。检测限为1．96×10^-6mol／L。成功用于样品的测定。     

聚苯胺修饰电极对甲醇的电催化氧化研究

应用电化学方法制备了Pt/PAn/GC电极,优化了苯胺在玻碳电极上的聚合条件,并对其进行了表征.结果表明,铂微粒在聚苯胺膜电极上具有很高的分散度,电极具有很大的比表面积,Pt/PAn/GC电极对甲醇电氧化的催化活性明显高于Pt/GC电极和Pt电极,在该电极上甲醇正向扫描和反向扫描时的氧化峰电流为58.68mA/cm2和50.00mA/cm2,为Pt/GC电极的1.6倍和1.7倍,为Pt电极的3.0倍和3.1倍,从而有效地提高了铂的催化活性,并得到在玻碳电极上聚合苯胺的最佳条件为扫描速度50mV/s,扫描上限1.2V.     

Effect of microstructure on the electrochemical behavior of Pt/YSZ electrodes

Two types of O₂,Pt/YSZ electrode preparation (Pt/YSZ cermet and sputtered platinum film) have been characterized by SEM and by cyclic voltammetry and chronoamperometry at 450 °C in 20 kPa oxygen. Cyclic voltammetry on the cermet and on the as-sputtered non-porous film electrode evidenced the characteristics of the PtO _x /Pt couple. The corresponding redox reaction occurs at the metal/electrolyte interface and it manifests itself by an anodic wave and one of more cathodic peaks in the voltammogram. Heat treatment of the sputtered electrode at 700 °C in oxygen atmosphere resulted in a porous structure by coalescence of the film. Cyclic voltammetry of the porous film electrode featured the characteristics of the O₂/O²⁻ couple, i.e. the redox reaction of gaseous oxygen occurring at the tpb. Chronoamperometry at anodic potentials showed similar features for both electrode preparations: an initial inhibition, a current peak and a slow activation, the latter being related to the phenomenon of electrochemical promotion of catalysis.     

在铂电极上循环伏安法氧化二甘醇研究

用循环伏安法研究了含二甘醇的１０ｍｏｌ·Ｌ－１Ｈ２ＳＯ４溶液在铂电极上的电氧化行为,证明它是一个不可逆的复杂的氧化还原过程,并考察了温度和浓度对该过程的影响。     

Cyclic voltammetry investigation of borohydride oxidation at a gold electrode

Sodium borohydride (NaBH₄) is receiving increasing attention during the last decade regarding its possible application in energy systems. NaBH₄ has the dual potential of generating hydrogen on demand or being directly oxidised in a direct borohydride fuel cell (DBFC). Progress on DBFCs relies on the development of systematic studies to allow a more comprehensive characterisation of the borohydride (BH₄⁻) oxidation process. In this paper, cyclic voltammetry (CV) is applied to study systematically the BH₄⁻ electrooxidation on a gold (Au) disc macroelectrode in 2 mol l⁻¹ NaOH solutions. Voltammograms are obtained for various NaBH₄ concentrations [0.03-0.12 mol l⁻¹], working temperatures [25-65 °C], and potential scan rates [0.02-20 V s⁻¹], over a wide potential range [−1.0-0.8 V vs. SCE]. Modelling of CV data indicates that BH₄⁻ oxidation on Au electrode follows a first irreversible electrochemical pathway via the direct BH₄⁻ oxidation reaction, involving nearly 8 mol of exchanged electrons per mole of BH₄⁻. A second pathway, at higher potentials, concerns a yet undetermined oxidation mechanism in the partially oxidised Au surface which, in a third pathway, is reactivated, allowing an electrochemical-adsorption mechanism to take place. Relevant parameters such as transfer coefficient, kinetic rate constant, standard rate constant, charge transfer activation energy, and number of exchanged electrons are estimated. The BH₄⁻ oxidation reaction on Au is found to be first order with respect to BH₄⁻.     

新型钛基银电极上硼氢化钠的电化学氧化

利用水热法,以聚乙二醇为还原剂将硝酸银还原, 产生的金属银颗粒直接沉积于钛表面,制备出具有三维网状结构的新型钛基银电极 (Ag/Ti)。利用循环伏安（CV）技术研究了碱性溶液中,Ag/Ti对硼氢化钠氧化的电催化活性。结果表明,硼氢化物在Ag/Ti电极上的氧化属直接电化学氧化过程,Ag/Ti电极对硼氢化物的电化学氧化表现出极高的电流密度,并且硼氢化物氧化的起始电位较低,约为-0.64 V vs SCE,说明Ag/Ti电极对硼氢化物氧化具有高度的电催化活性,有望作为硼氢化物燃料电池的阳极材料而得到应用。     

Effect of KOH concentration in the gel polymer electrolyte for direct borohydride fuel cell

The performance of a direct borohydride fuel cell (DBFC) based on a polyacrylamide (PAAm) gel polymer electrolyte system is investigated at different electrolyte concentrations. The DBFC, constructed using 2M sodium borohydride (NaBH₄) as the fuel and potassium hydroxide (KOH) solution gelled with PAAm as the electrolytes yield the highest electrical conductivity of 2.73 × 10^?1 S cm^?1 at 6M KOH. The optimized composition, PAAm + 2M NaBH₄ + 6M KOH, and the selected composition, PAAm + 2M NaBH₄ + 3M KOH are then used in preparing the cells. Open‐circuit voltages for fuel cells is about 0.85–0.92 V, and the discharge characteristic produce discharge capacities of about 257.12–273.12 mAh cm^?2 for cells with PAAm‐6M KOH. Current‐voltage and current density‐power density plots and internal resistance for both cells are almost the same. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Decolorization of meadowfoam estolides using sodium borohydride

Estolides are condensed oligomers of fatty acids made by introducing an ester linkage at sites of unsaturation. Estolides made from meadowfoam (Limnanthes alba) oil fatty acids have positive effects in personal care formulations and a patent has been applied for. However, estolides prepared by acid catalysis had a color of 12 (Gardner scale) and industrial cooperators desired lower color to increase marketability of meadowfoam estolides. Hydrogen peroxide and hydrogenation did not lower the color of estolide but 1% w/w sodium borohydride at 80°C for 12 h reduced color to 7 on the Gardner scale which was acceptable to the industrial partners for further development. Sodium borohydride decolorization gives a product with good color at a reasonable cost. The sodium borohydride does not have to be used in concentrations higher than 1% w/w and the product loss, which can be several percent with a clay-based process, is negligible using sodium borohydride.     

硼氢化钠在氢氧化钠溶液中的密度和黏度

在291、298、303 K下,将不同质量的硼氢化钠固体分别加入到质量分数为13.35%的氢氧化钠溶液中,用密度瓶法和Ubbelohde黏度管分别测量溶液密度和黏度。根据溶液的密度计算硼氢化钠溶液的表观摩尔体积,讨论浓度的变化对混合溶液密度的影响,可知随着硼氢化钠浓度的加大,密度逐渐减小。根据溶液黏度数据和BH4- 半径计算了不同温度下硼氢化钠和BH4- 的黏度系数B,结果表明,BH4- 是结构促进型离子,且随着温度升高,黏度系数B逐渐减小。     

复分解法制备硼氢化钾

为了减少Schlesinger法生产固体硼氢化钠的母液循环所带来的水解损失和设备负荷,以目前工业硼氢化钠生产中典型结晶母液(25%Na BH4、5%Na OH、70%H2O)和氢氧化钾为原料,采用复分解法直接制备固体硼氢化钾。利用X-射线粉末衍射、光学显微分析和碘量滴定法研究了氢氧化钾用量、反应温度、结晶温度、溶剂蒸发量等因素对产品组成和收率的影响。结果表明,氢氧化钾/硼氢化钠摩尔比为1.10,反应温度低于60℃,结晶温度低于10℃时,硼氢化钾粗产品粒度分布均匀,纯度可以达到86%,收率80%。     

Evaluation of the electrochemical properties of 3-hydroxyflavone using voltammetric methods

Electrochemical behavior of ring C of 3-hydroxyflavone (3-HF) has been investigated by cyclic and differential pulse voltammetry, using a glassy carbon electrode (GCE) in different buffer systems. It exhibited a sensitive diffusion controlled anodic peak at 0.70 V (vs Ag/AgCl) in a buffer system at pH 2.0. At higher pH, 8.0, while the peak at 0.70 V shifted to 0.41 V, a new peak at 0.8 V appeared. Moreover, electrochemical method was applied to investigate the antioxidant effect and metal chelating properties of 3-HF with Cd²⁺, Cu²⁺, Hg²⁺ and Pb²⁺ as they could have possible toxicological effects, for which fluorescence technique were also applied. Antioxidant effect was determined in terms of trolox equivalent antioxidant capacity (TEAC) using the peak areas of cyclic voltammetry (CV), which indicated that 1.0 mM 3-HF is equivalent to 0.2 mM of trolox. Such a result might be another indication of the importance of hydroxyl groups on the other rings of flavones. Electrochemical and fluorescence spectroscopic methods revealed that the best interactions of the cations could be obtained depending on the pH of the medium. Selective interactions of Cd²⁺ and Cu²⁺ at pH 2 and 7, respectively, were observed.     

Determination of kinetic parameters for borohydride oxidation on a rotating Au disk electrode

Borohydride oxidation has been investigated using a rotating disk electrode technique. The parameters, such as apparent rate constant, Tafel slope, Levich slope, number of electrons exchanged and reaction order, have been determined. The borohydride ion is oxidised on the gold electrode with an electrochemical rate constant of around 1 cm s⁻¹ at intermediate potentials where side reactions had less effect. Influences of temperature, concentrations of borohydride and supporting electrolyte (NaOH) on the parameters were evaluated.