Enhanced electrochemical activity of Pt nanowire network electrocatalysts for methanol oxidation reaction of fuel cells

In this work, Pt nanowire networks supported on high surface area carbon (Pt NWNs/C) are synthesized as electrocatalysts for direct methanol fuel cells (DMFCs). The electrocatalytic behavior of Pt NWNs/C catalysts for the methanol and adlayer CO oxidation reactions is investigated and the results are compared with the Pt nanoparticles (NPs) supported on carbon (Pt NPs/C). The results indicate that Pt NWNs are characterized by interconnected nanoparticles with large number of grain boundaries, downshifted d-band center and reduced oxophilicity, which results in the enhanced surface mobility of oxygen-containing species such as CO_ads and OH_ads. The enhanced surface mobility of CO_ads and OH_ads in turn facilitates the removal of intermediate CO species during the methanol oxidation. The activity of the Pt NWNs/C electrocatalyst for the methanol oxidation reaction and electrooxidation of adsorbed CO is also evaluated by cyclic voltammetry, CO stripping, and kinetic analysis. The results show that Pt NWNs/C catalysts have a significantly higher electrocatalytic activity for the methanol oxidation reaction as compared to Pt NPs/C catalysts. The enhanced electrocatalytic activity of Pt NWNs/C catalysts is mainly due to the existence of large number of the grain boundaries of the interconnected nanoparticles of the unique Pt NWN structure.     

Effects of 1,3-dialkylimidazolium cations with different lengths of alkyl chains on the Pt electrode/electrolyte interface in dye-sensitized solar cells

The electrochemical behaviors of the tri-iodide (I₃⁻)/iodide (I⁻) redox couple of symmetric cells were investigated by cyclic voltammetry, steady-state polarization, chronocoulometry, and electrochemical impedance spectroscopy. 1,3-Dialkylimidazolium cations affected the characteristics of the Pt electrode/electrolyte interface by adsorbing on the Pt electrode, as a result of electrostatic interactions, and further affected the reduction of I₃⁻ on the Pt electrode. Capacitance of the double layers of the Pt electrode/electrolyte interface was chiefly determined by capacitance of the compact layer according to the Helmoholtz theory.     

Magnetron sputtering of platinum nanoparticles onto vertically aligned carbon nanofibers for electrocatalytic oxidation of methanol

The electrochemical activities of Pt-sputtered electrodes based on vertically aligned carbon nanofibers (Pt/VACNFs) directly grown on the carbon paper are investigated. Different Pt loading (0.01 mg cm⁻², 0.025 mg cm⁻² and 0.05 mg cm⁻²) electrodes are developed. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the Pt nanoparticles are homogeneously dispersed on the surface of vertically aligned carbon nanofibers. TEM and X-ray diffraction (XRD) results reveal the Pt nanoparticles diameter increase with increasing Pt loading. The Pt/VACNFs electrodes show good electrochemical active surface area, methanol oxidation peak current density and CO tolerance. The electrochemical catalyst activities weaken as the diameter grows larger. Compared to common electrodes prepared by commercial catalyst in a conventional ink-process, the performance improvement suggests that unique structure of Pt/VACNFs electrode ensures the electronic pathway and Pt nanoparticles exposed to three-phase boundary, which leads to a significant improvement of the Pt utilization and a potential application in direct alcohol fuel cells.     

异丁烷脱氢Pt系催化剂研究进展

介绍异丁烷脱氢制备异丁烯Pt系催化剂的研究进展,表明催化剂的活性中心、载体和助剂对异丁烷脱氢反应性能影响较大。催化剂活性中心的积炭覆盖和烧结是催化剂失活的直接原因;载体的酸性有助于调变积炭的形成速率,而活性中心与助剂的交互作用可促使积炭的表面迁移;活性中心与载体的交互作用有利于减少活性中心的烧结。     

Na改性Pt/AlOOH对甲醛催化氧化反应活性的影响

具有晶面取向的阳极氧化AlOOH因其低温甲醛催化性能而被用于催化氧化甲醛体系。为丰富AlOOH表面羟基含量,采用Na₂CO₃为Na前体浸渍法改性载体,制备不同Na含量（0.13%、0.19%、0.30%、0.41%,质量分数）的Pt/Na_x/AlOOH催化剂。通过BET、FTIR、XPS、HRTEM等表征分析,发现加入Na后,Na/AlOOH的表面羟基更加丰富,Pt/Na_x/AlOOH催化剂的比表面积增大,拥有更小的Pt颗粒尺寸,表面Pt颗粒分散度提高,Pt0元素价态含量增加。当Na含量为0.41%时,催化剂Pt/0.41Na/AlOOH的Pt分散度高达56%。实验结果证明,Pt/0.41Na/AlOOH展现出最优的HCHO催化活性,60℃时HCHO转化率达100%。     

In situ generation of hydrogen peroxide and its use for enzymatic degradation of 2,4,6‐trinitrotoluene

A novel electroenzymatic method hybridizing both electrochemical and enzymatic reactions and using lignin peroxidase (Lip) for treatment of TNT (2,4,6‐trinitrotoluene) waste was studied. In the presence of Phanerochaete chrysosporium lignin peroxidase, TNT was degraded in an electrochemical reactor using hydrogen peroxide, produced by an electrode reaction. The effectiveness of the electroenzymatic method was examined in this study. The efficiency of removal of TNT was greater than that of biochemical methods under optimal conditions. The effects of reaction conditions on TNT degradation and denitrification, TOC removal efficiency, and power consumption were also investigated. A potential (vs Ag/AgCl) of +0.1 V was selected as being optimal for the electroenzymatic reaction. TNT degradation was significantly improved in the combined veratryl alcohol–lignin peroxidase oxidation procedure, showing complementary effects of veratryl alcohol (VA) in the TNT degradation reaction. Denitrification was found to be proportional to the amount of TNT degraded. One intermediate, 2,4‐diamino‐6‐nitrotoluene, derived from the oxidative degradation of TNT, was eluted on an HPLC chromatogram and was detected using mass spectrometry. The electroenzymatic method had a lower power requirement than electrochemical oxidation at ?0.2 and ?0.4 V. The electroenzymatic method may be easily applied to biodegradation systems and provide added benefit for highly recalcitrant chemicals since the system would not be susceptible to the toxicity of the chemical. Also H₂O₂ instability and decomposition in the samples after preparation would not be of concern. © 2001 Society of Chemical Industry     

柴油车DOC催化剂Pt/CeZrO2载体的制备及影响

分别用氢氧化钠（NaOH）、草酸（H₂C₂O₄）和碳酸钠（Na₂CO₃）为沉淀剂制备CeZrO₂固溶体,并以此为载体制备了Pt/CeZrO₂柴油车DOC催化剂,通过XRD、BET、H₂-TPR和催化氧化反应等手段对催化剂物理化学特性进行研究。结果发现,以NaOH作为沉淀剂制备的CeZrO₂固溶体比表面积大（68.8 m²·g^-1）、氧活动性强[表面氧耗氢量达1143 μmol·（g cat（^-1],同时贵金属Pt在其表面高度分散,因此制得的Pt/CeZrO₂柴油车DOC催化剂催化效果好,特别是催化氧化碳氢化合物（C₃H₆）,T₉₀比H₂C₂O₄和Na₂CO₃为沉淀剂制备的Pt/CeZrO₂催化剂降低了将近40℃。另外载体制备方式对催化剂抗硫性影响也十分显著。故选择一种合适的载体沉淀剂可使制得的DOC催化剂具备良好的活性及抗硫性。     

从铂钯精矿中回收贵金属工艺选择

概述了金、银、铂、钯回收提纯的有关化学反应原理,拟定了从铂钯精矿中回收金、银、铂、钯的工艺流程,采用硫酸化焙烧,酸浸除贱金属,富集贵金属,再氯化分别提取贵金属,获得了满意的生产指标,金属回收率分别为:Au 98.1%,Ag97.2%,Pt93.0%,Pd95.6%.     

电解制备离子水的研究

研制了一种简易的离子水生成器 ,采用电解法制备酸性离子水和碱性离子水。比较分析了电极材料的性能 ,发现阳极和阴极同时采用铂 /钛合金 ,电解性能较好。Na Cl浓度和电解时间不同 ,所制得的离子水强度也不同 ,Na Cl浓度宜选择 0 .5～ 1 .0 g/ L。同时 ,制得的离子水应密封保存     

静电自组装质子交换膜燃料电池用膜电极的光谱学分析

合成了一种季铵聚阳离子(PDDA)修饰的纳米Pt颗粒,采用静电自组装的方法将这种颗粒组装到质子交换膜(PEM,Nafion112)表面,Pt粒子的表面原子状态、Pt的还原和自组装过程以及自组装膜的电化学性能分别采用傅里叶转换红外(FTIR)、紫外-可见吸收光谱(UV-vis)和电化学工作站分析。结果表明,较低的修饰离子含量有利于提高还原速度和增加Pt粒子的表面裸露原子数量,n(PDDA)∶n(Pt)=5∶3为合适的修饰离子用量;发现静电自组装是一个先由大量的小阳离子占据空位,然后由带电大颗粒取代的过程,该体系的自组装在12h完成,此后Pt的组装量(3 2×10-3mg/cm2)和膜的导电能力(0 02S/cm)不再改变。