三氧杂环己烷的电化学特性

直接氧化一些有机小分子(如甲醇[1~9]和乙醇[10~14]等)的直接氧化燃料电池作为一种对环境友好的能源越来越引起人们的关注.三氧杂环己烷作为一种可再生的能源,可以从地球上存在的大量天然气中得到,来源广泛,价格低廉.三氧杂环己烷反应的基本结构如Scheme 1所示,相对乙醇而言,三氧杂环己烷不存在任何碳碳键,反应更易进行.目前广泛研究的直接氧化燃料电池均采用液体甲醇和S chem e 1 S tru ctu re of tr ioxane乙醇等作燃料,液体燃料的存储运输存在一定的安全隐患,一旦泄漏发生危险,后果非常严重,而三氧杂环己烷作为一种固体,可以有效地避免上述问题的发生,利于安全的储存和运输.Narayanan等[13]研究了三氧杂环己烷在Pt,Pt-Sn和Pt-Ru电极上的电化学行为及其在燃料电池中的应用.本文研究了三氧杂环己烷在不同浓度、不同温度和不同酸度时于光滑铂电极上的电化学行为,初步分析了三氧杂环己烷的反应机理.1实验部分1.1试剂与仪器采用Potentiostat/GalvanostatModel 273A恒电位仪(美国Princeton Applied Research公司),在传统的三...

一种新型直接甲醇燃料电池阳极添加剂的电化学研究

将磷钼酸 (H4PMo12 O40 ·xH2 O ,PMo12 )作为一种添加剂 ,制备了直接甲醇燃料电池阳极Pt Ru/C PMo12 复合催化剂 ,并对甲醇在含有此复合催化剂的阳极上的氧化进行了电化学研究 .测试表明该添加剂降低了甲醇及其电氧化中间产物转化的活化能 ,改善了电极内部的质子传输状况 ,对甲醇的电化学氧化过程具有明显的促进作用 ,该复合催化剂与常规的Pt Ru/C催化剂相比 ,甲醇的阳极氧化电流提高了 46% .添加剂的这一效应可能与磷钼酸的Keggin结构有关

碳纳米管负载铂催化剂的制备及其对甲醇的电催化氧化研究

Pt金属是直接甲醇燃料电池(DMFC)常用的催化剂犤1～3犦。为了尽可能减少Pt金属用量,提高Pt的分散度,人们总是选择具有高表面积的基质,如石墨、碳黑、活性碳、分子筛、质子交换膜等,作为Pt金属的载体犤3～5犦。最初,人们以为载体的作用仅仅是提供表面积和多孔气体扩散电极的骨架,使Pt微粒可以有更大的比表面积与反应物接触,但是现在普遍认为犤1犦,当Pt金属负载在活性炭上时,它们中的催化性能有一部分应归结于金属和载体之间的相互作用,因此,载体的形貌及物理化学性质直接影响着催化剂对甲醇的电催化氧化活性。碳纳米管(CNTs)由于其拥有纳米级管腔结构、较高的比表面积、类石墨的多层管壁等特点,使它在做催化剂载体方面有着良好的应用前景犤6～9犦。CheGuangli等人犤6犦在探索CNTs的潜在用途时,曾研究了将Pt、Ru、PtRu等金属或合金沉积在CNTs的内壁,并讨论了其在DMFC上的潜在用途。本文通过液相化学还原的方法制得Pt载量为20%的Pt/CNTs催化剂,并研究了预处理对催化剂形貌、表面基团及其对甲醇电催化氧化性能的影响。1实验部分1.1试剂和仪器实验所用试剂均为分析纯,所有溶液均用三次蒸馏水配制。

铂、钌共修饰的氧化钛电极对甲醇的电催化氧化

首次发现用电化学阴极还原 -阳极氧化法制得的 Pt-Ti Ox/Ti和 Pt-Ru-Ti Ox/Ti电极对甲醇氧化呈现出较高的电催化活性和稳定性 ,其中 Pt-Ru-Ti Ox/Ti电极比 Pt-Ti Ox/Ti电极具有更好的性能 .实验结果表明 ,这两种电极对甲醇氧化具有高电催化活性是由于 Pt、Ru得到了较好的分散 ,较好的稳定性可归结于Pt、Ru与 Ti Ox 协同作用导致弱的 CO吸附而使电极不易中毒 .

滇西菲红超基性岩风化壳铂族元素地球化学行为

近年来在世界不同地区进行了风化过程中铂族元素的地球化学行为研究。作为中国西南部的第一个实例． 本文研究了云南西部菲红超基性岩体上发育的红土化风化剖面。矿物学和微量元素地球化学研究证明该风化壳 是超基性岩风化的结果。文中详细讨论了风化壳的地质、矿物学、红土化和铂族元素地球化学特征。结果表明， 风化壳的红土化程度不高，仍处于红色牯土阶段；风化壳上酃的表层土壤带和铁质牯土带中铂族元素总量至少富 集了3 57—7．盯倍，其中Ru和Pd的富集程度较大，Ix的富集程度中等，Pt和弛的富集程度较小，使得铂族元素 的配分模式由基岩的Pt富集型转变为风化壳的Ru-Pt富集型，证明红土化过程中铂族元素发生了分异。

Determination of ionic resistance and optimal composition in the anodic catalyst layers of DMFC using AC impedance

In the present study, a method based on transmission-line mode for a porous electrode was used to measure the ionic resistance of the anode catalyst layer under in situ fuel cell operation condition. The influence of Nafion content and catalyst loading in the anode catalyst layer on the methanol electro-oxidation and direct methanol fuel cell (DMFC) performance based on unsupported Pt-Ru black was investigated by using the AC impedance method. The optimal Nafion content was found to be 15 wt% at 75 degrees C. The optimal Pt-Ru loading is related to the operating temperature, for example, about 2.0 mg/cm(2) for 75-90 degrees C, 3.0 mg/cm2 for 50 degrees C. Over these values, the cell performance decreased due to the increases in ohmic and mass transfer resistances. It was found that the peak power density obtained was 217 mW/cm(2) with optimal catalyst and Nafion loading at 75 degrees C using oxygen. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Performance comparison of low-temperature direct alcohol fuel cells with different anode catalysts

Low-temperature polymer electrolyte membrane fuel cells directly fed by methanol and ethanol were investigated employing carbon supported Pt, PtSn and PtRu as anode catalysts, respectively. Employing Pt/C as anode catalyst, both direct methanol fuel cell (DMFC) and direct ethanol fuel cell (DEFC) showed poor performances even in presence of high Pt loading on anode. It was found that the addition of Ru or Sn to the Pt dramatically enhances the electro-oxidation of both methanol and ethanol. It was also found that the single cell adopting PtRu/C as anode shows better DMFC performance, while PtSn/C catalyst shows better DEFC performance. The single fuel cell using PtSn/C as anode catalyst at 90degreesC shows similar power densities whenever fueled by methanol or ethanol. The cyclic voltammetry (CV) and single fuel cell tests indicated that PtRu is more suitable for DMFC while PtSn is more suitable for DEFC. (C) 2003 Elsevier B.V. All rights reserved.

NOx storage-reduction over Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios

A series of Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios were prepared. The NOx storage capacities of these catalysts were measured by isothermal storage at 350 degreesC. It was found that the NOx storage capacity increased with increasing Mg/Al atomic ratios. The catalytic behaviors of Pt/Mg-Al-O and Pt/MgO were studied with storage-reduction cycles at 400 degreesC. Under oxidizing conditions, NOx concentration in the outlet gas gradually increased with time, which indicated the catalysts could store NOx effectively. After a switch from oxidizing conditions to reducing conditions, NOx desorption peak emerged immediately due to the incomplete reduction of stored NOx, which lowered the total NOx conversion. With increasing Mg/Al atomic ratio in the catalysts, NOx conversion increases. Pt/MgO has the highest NOx conversion because of its best activity in the reduction of NOx by C3H6. It seems that with an increasing amount of MgO in the catalysts, the self-poisoning of Pt-sites by adsorbed species during the reaction of NOx with C3H6 may be inhibited effectively.

Studies on state and structure of noble metals in electrocatalyst made by coprecipitation method

The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X-ray diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide-form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.

Multi-walled carbon nanotubes supported Pt-Fe cathodic catalyst for direct methanol fuel cell

Multi-walled carbon nanotubes supported Pt-Fe cathodic catalyst shows higher specific activity towards oxygen reduction reaction as compared to Pt/MWNTs when employed as cathodic catalyst in direct methanol fuel cell.