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通过阴极还原-阳极氧化法制备了钛基纳米铂微粒修饰电极, 扫描电镜观察发现, 分布于钛基体表面的氧化钛膜三维网状孔道中的纳米铂微粒具有高度分散状态. 采用多种电化学手段在该电极上不仅观察到甲醛在恒电流条件下产生的电位振荡, 而且在循环伏安和恒电位两种条件下均观察到强烈的电流振荡, 这进一步证明高度分散的纳米铂微粒使电极的催化活性大大提高, 促进了甲醛及其毒化中间产物的电催化氧化过程, 从而有利于电极上电化学振荡的产生. 研究结果还表明, 甲醛底物浓度、硫酸介质浓度、恒电位或恒电流大小等多种因素对振荡强度、范围或类型会产生规律性的影响. 相似文献
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采用电化学石英晶体微天平(EQCM)研究了0.5 mol•L-1 NaOH水溶液中铂电极上葡萄糖、半乳糖和乙醇恒电流氧化过程中伴随的电位振荡行为. 两个糖体系的电位振荡过程伴随EQCM频率的同步振荡响应, 而乙醇体系中相应的频率响应却非常小;三个体系振荡过程的同步动态电阻响应均很小, 表明振荡过程频率响应主要为质量效应. 虽然葡萄糖和半乳糖结构相似, 电位和频率振荡的幅度相当, 但频率波数和周期明显不同, 表明电位振荡行为对两者呈现良好的分子识别能力. 本文也讨论了相关振荡机理和NaOH浓度效应及碱性介质中铂电极电化学过程, 提出了所形成的铂氧化物主要是PtO2-3H2Oad以及两糖体系振荡过程中糖酸根阴离子伴随着高/低电位在铂电极上吸/脱附的新观点. 相似文献
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在5 mmol/L H2 PtCl6的稀硫酸溶液中,采用循环伏安法(CV),扫描电位为~0.2~0.6V和0.0~0.6v,分别扫描30和15循环,在碳纳米管/纳米TiO2-聚苯胺复合膜上实现了Pt纳米粒子的高度有效分散,得到多壁碳纳米管/纳米TiO2-聚苯胺载铂四组分纳米结构复合电极,通过CV法和计时电位法并结合扫描电镜对复合电极的电化学性质和结构进行表征,研究了复合电极对葡萄糖的电催化氧化性能.结果表明,该复合电极对葡萄糖的电氧化有高催化活性,具有性能稳定、重现性好、抗毒化作用强、能耐高温、易保存且使用寿命较长的优点. 相似文献
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本文介绍一种由各自质子交换膜(作为电解质),参比电极和对电极在同一个工作电极上建立两个空间分离的、可独立控制的双电解池系统.它能够由第1个恒电位仪控制的第1电解池的工作电极产生某种吸附中间物,该中间物通过表面扩散到达第2个电解池的工作电极后,在第2个恒电位仪的控制下得到电化学检验.应用这一装置测量了铂电极上欠电势沉积的含氧吸附物种的表面扩散系数,并研究模拟铂钌电极电氧化有机小分子产生的毒性中间物与表面含氧吸附物种的相互作用.在质子交换膜燃料电池的燃料极的工作电势下,没有发现钌表面产生的含氧吸附物种扩散到铂的表面.作者据此假设Pt Ru协同催化作用的实现可能是由于铂上毒性中间物的表面扩散速率非常慢,限制了向钌表面的溢流速率.只有当Pt Ru边界足够大,中间物在铂表面扩散途径非常短时才能形成足够的流速,并在钌表面被表面含氧物种氧化成CO2,使铂表面被重新活化. 相似文献
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用合适金属修饰的铂催化剂能够显著增强其对甲酸氧化的电活性.本文以水热法制备了钛负载的纳米多孔铂电极(nanoPt/Ti),然后采用循环伏安法,通过扫描不同的周数(n),用适量的铅对nanoPt/Ti电极进行修饰,得到一种新型的铅修饰的纳米多孔铂电极(nano Pb_((n))-Pt/Ti).采用循环伏安(CV)、计时电流和计时电位法研究其对对甲酸氧化的电活性.CV结果显示nanoPt/Ti和nanoPb_((n))-Pt/Ti电极对甲酸氧化表现出较高的催化活性,并且nanoPb_((20))-Pt/Ti电极对甲酸氧化的起始电位为-0.06 V,相比nanoPt/Ti电极的起始电位(0.06 V),明显有所负移.此外,nanoPb_((20))-Pt/Ti电极的第一个氧化峰电流密度为12.7 mA·cm~(-2),远远大于nanoPt电极(4.4 mA·cm~(-2));计时电流显示在电位为0.1 V时,在0.5 mol·L~(-1)H_2SO_4+1 mol·L~(-1 )HCOOH溶液中,nanoPb_((20))-Pt/Ti电极达到稳定时的电流为8.09 mA·cm~(-2),是nanoPt电极的60倍,表明铅修饰的nanoPt/Ti对甲酸氧化的电活性急剧增加;在1.5mA、2 mA、2.2 mA和2.5 mA下的计时电位结果表明,nanoPb_((20))-Pt/Ti电极上甲酸氧化过程表现出显著的电化学振荡,且和nano Pt/Ti电极相比,振荡现象能持续更长的时间,说明nanoPb_((20))-Pt/Ti电极具有更强的表面抗毒化能力. 相似文献
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采用常规电化学伏安技术和电化学原位表面增强拉曼光谱(in-situ SERS)技术研究了不同介质中乙醇在粗糙铂电极上的电催化氧化行为. 发现不论在酸性、中性还是碱性介质中, 乙醇均能在粗糙铂电极上自发氧化解离生成强吸附中间体CO; 碱性介质中, CO在粗糙铂电极上基本氧化完全的电位(0.20 V)比中性和酸性介质中(0.50 V)负移了约0.30 V. 而乙醇在粗糙铂电极上CV正向扫描的氧化峰电位(-0.20 V)比酸性介质中(0.65 V)负移了约0.85 V. 比较不同介质中乙醇和CO在粗糙铂电极上的氧化峰电流和峰电位可以发现, 粗糙铂电极在碱性介质中对乙醇和CO的电催化氧化活性比中性和酸性介质中更强; 可以推测, 不论在酸性、中性还是碱性介质中, 乙醇在粗糙铂电极上的氧化过程均按双途径机理进行. 相似文献
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The oxidation of glucose at low concentrations was studied at electrodeposited platinum electrodes in 0.1 M HClO4 using an electrochemical quartz crystal microbalance (EQCM). Experiments were performed over the whole potential range and then over selected regions of potential to investigate the processes giving rise to specific features in the cyclic voltammetry and mass response. In the region of potential where adsorbed hydrogen is present, EQCM experiments reveal the presence of adsorbate derived from glucose through the removal of features associated with the presence of adsorbed anions in the background electrolyte. Cycling over this potential region leads to a decrease in the mass of the electrode as the coverage of poisoning species increases. In the double-layer region of potential an increase in mass is seen as the adsorbate is oxidized and removed from the electrode surface, and is suggested to be a result of the replacement of adsorbed residues (formed from progressive oxidation of glucose) by both anions and fresh reactant. Restriction of the electrode potential to values above 0.2 V (SCE) prevents poison formation and mass responses indicate the presence of adsorbed glucose between 0.2 V and 0.6 V. Mass responses accompanying voltammetry and injection experiments also indicate that glucose or species derived from it can adsorb on an oxidized platinum surface. 相似文献
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鲁米诺在铂电极上阳极电致化学发光的机理研究 总被引:1,自引:0,他引:1
研究了碱性鲁米诺溶液在多晶铂电极上的阳极电致化学发光(ECL)行为,观察到电极的预极化处理和溶解氧跟发光峰强度和峰形有直接关系。结合XPS谱图和Pt,Pt|S~a~d~s修饰电极的循环伏安特性,给出了鲁米诺阳极ECL两个发光通道的可能反应机理:(1)鲁米诺阴离子在表面有新鲜Pt原子的电极上氧化生成鲁米诺自由基,然后迅速与溶液中的氧反应形成0.22V(vs.Ag)处的发光肩峰;(2)电极表面的铂氧化物能加速原子态氧的发生过程,并增大0.60V(vs.Ag)附近ECL主峰的发光强度。 相似文献
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有机小分子电极氧化过程中的振荡现象已作为非线性电极过程复杂体系动力学的一个典型实验进行了研究[1,2].Shel等报道了有机小分子电极氧化循环伏安曲线的振荡[3~5],表面上吸附物质或膜的生成与消耗是导致振荡乃至混沌行为发生的原因.在低NaOH浓度时... 相似文献
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The oxidation pathways of methanol (MeOH) have been the subject of intense research due to its possible application as a liquid fuel in polyelectrolyte membrane (PEM) fuel cells. The design of improved catalysts for MeOH oxidation requires a deep understanding of these complex oxidation pathways. This paper will provide a discussion of the literature concerning the extensive research carried out in acidic and alkaline electrolytes. It will highlight techniques that have proven useful in the determination of product ratios, analysis of surface poisoning, anion adsorption, and oxide formation processes, in addition to the effects of temperature on the MeOH oxidation pathways at bulk polycrystalline platinum (Pt(poly)) electrodes. This discussion will provide a framework with which to begin the analysis of activation energy (E(a)) values. This kinetic parameter may prove useful in characterizing the rate-limiting step of the MeOH oxidation at an electrode surface. This paper will present a procedure for the determination of E(a) values for MeOH oxidation at a Pt(poly) electrode in acidic and alkaline media. Values from 24-76 kJ mol(-1) in acidic media and from 36-86 kJ mol(-1) in alkaline media were calculated and found to be a function of applied potential and direction of the potential sweep in a voltammetric experiment. Factors that influence the magnitude of the calculated E(a) include surface poisoning from MeOH oxidation intermediates, anion adsorption from the electrolyte, pH effects, and oxide formation processes. These factors are all potential, and temperature, dependent and must clearly be addressed when citing E(a) values in the literature. Comparison of E(a) values must be between systems of comparable electrochemical environment and at the same potential. E(a) values obtained on bulk Pt(poly), compared with other catalysts, may give insight into the superiority of other Pt-based catalysts for MeOH oxidation and lead to the development of new catalysts which lower the E(a) barrier at a given potential, thus driving MeOH oxidation to completion. 相似文献
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UPD铅对甲酸在铂上电氧化的助催化功用的研究 总被引:1,自引:0,他引:1
应用电位扫描和电位-时间程序技术研究了在UPD铅不存在和存在的情况下,各种因素对甲酸在铂上和酸介质中电催化氧化的影响。结果表明,在甲酸的CV图上,阳极方向的第一氧化峰和阴极方向的氧化峰是由于同一的弱吸附中间物的氧化,而阳极方向的第二和第三氧化峰是由于两种不同的强吸附中间物的氧化。cps值的测定和电极表面宏观结构的影响等实验表明,这些吸附中间物在电极表面上都呈线性吸附,它们分别可能是单键吸附的HCOOad双键吸附的COad和叁键吸附的COHad。据此可以推论,UPD铅的主要功用是一种电子效应。 相似文献
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A novel Ti-supported gold catalyst (nanoAu/Ti) with a nanoporous 3D texture has been fabricated using a hydrothermal method. Au particles were stably deposited on the Ti surface from the mixture of aqueous tetrachlororoauric acid and polyethylene glycol at 180 °C. Voltammetry (CV) and chronoamperometry were used to characterize the nanoAu/Ti electrode and assess its electroactivity towards glucose oxidation. Compared to polycrystalline Au, the nanoAu/Ti electrode shows similar CV profiles in alkaline solution. However, in an alkaline solution containing 10 mM glucose, the nanoAu/Ti electrode presents much higher anodic current densities and a more negative onset potential (ca. ?0.75 V) for glucose oxidation than a bulk Au electrode. Analysis for Tafel plot of the nanoAu/Ti electrode shows that electro-oxidation of glucose takes place via a one-electron rate-determining step. Results indicate a high and (relatively) stable electrocatalytic activity of the nanoAu/Ti for glucose oxidation. 相似文献
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乙醇和甲醇在含钼碱性溶液中的铂黑电极上氧化时,在一定条件下可得到循环伏安曲线的周期性及非周期性振荡.通过微调下限电位可控制振荡的周期,其中非周期性振荡具有混沌的特性.讨论了钼的存在及碱浓度的变化对振荡的影响.结果表明,钼的氧化还原振子在电极表面与小分子醇的氧化过程中发生耦合作用是导致振荡的关键 相似文献