热氧化制备的钯氧化物电极的组成与pH敏感性能

用钯氧化物电极作pH敏感元件已引起人们的兴趣^[1～3],但对其性能及其与制备条件的关系仍缺乏了解。本文着重讨论热氧化制备的钯氧化物电极的组成和pH敏感性能同氧化温度的关系。     

一步法制备钯纳米粒子修饰的多孔金电极及其对溶解氧的电催化

建立了只需一步操作即可完成在抛光洗净的金微盘阵列电极上进行多孔化处理和钯纳米粒子修饰的方法。通过对金微盘电极连续施加3个电位,分别实现金的氧化、金的还原和电沉积钯纳米粒子。利用扫描电镜和电化学方法监控制备过程,得到的结果证实了本方法的可行性和有效性。考察了溶液pH值与氧化时间对结果的影响,在磷酸盐缓冲溶液(pH7)中氧化90s,得到的修饰电极的电化学活性面积是裸电极的42倍。同时,由于整个过程不需要更换溶液,且只需开启一次仪器,大大简化了实验操作。将制备的修饰电极用于溶解氧的电催化,对溶解氧的灵敏度达到0.1mA·L/(cm2·mg),优于文献报道结果。     

高阳极电势窗口的SnO2-Sb2O3/Ti电极的制备

制备了不同热处理温度和涂层次数的SnO2-Sb2O3/Ti电极,研究了不同电极涂层的氧化物组成,涂层表面形貌和阳极电势窗口及其三者的内在关系,考察了不同制备工艺条件的电极对电催化高铁性能的影响.结果表明430℃是电极最佳的热处理温度,涂层次数增加为30次时,电极具有高的阳极电势窗口,同时能降低高铁氧化还原反应的超电势,更真实的展现高铁电化学生成的热力学原貌.     

导电氧化物电极上丁酸丁酯电化学合成的研究

本文研究了某些氧化物电极在不同条件下对丁醇电解直接合成丁酸丁酯的影响，并测定了这些氧化物电极上的丁醇氧化极化曲线，结果表明Ｔｉ／ＰｂＯ２电极在加入ＳｎＯ２，Ｓｂ２Ｏ３，ＰｄＯｘ中间层后，不仅电极的ＰｂＯ２层不易脱落，而且使电极的电催化性能有较大的提高。     

六氰合铁酸锰铬修饰电极的制备及其电化学行为

应用循环伏安法在活化玻碳电极(GCE)表面制备六氰合铁酸锰铬(MnCrHCF)膜修饰电极(MnCrH-CF/GCE)并研究其电化学性质.探讨影响膜电沉积的因素,研究pH值以及不同支持电解质等制备条件对该修饰电极性能的影响,优化制备工艺,分析其反应机理.     

Ni-Ru-Ir氧化物阴极涂层的析氢活性

应用热分解氧化法制备Ni-Ru-Ir氧化物活性阴极.循环伏安、Tafel曲线及计时电流测试表明,在90℃、30%(bymass)的NaOH溶液中,电流密度0.3A·cm-2条件下,Ru∶Ir质量比为1∶1的Ni-Ru-Ir氧化物电极的析氢过电位比Ni电极低300mV;表面粗糙度是Ni网电极的32倍;交换电流密度是Ni网电极的4倍;其析氢性能显然远优于Ni网电极,有望应用于氯碱工业以期降低能耗.     

钛基金属氧化物电极制备及降解甲基橙研究

采用高温热氧化法制备Ti/Sn-Sb,Ti/Sn-Sb-Mn,Ti/Sn-Sb-Co,Ti/Sn-Sb-Pb氧化物电极,通过扫描电镜、析氧电位测定、加速寿命试验等方法考查各电极的表面形貌、析氧电位和使用寿命,并对四种电极降解偶氮染料甲基橙溶液的情况进行比较。结果表明Ti/Sn-Sb-Pb氧化物电极具有较长的使用寿命和较好的电催化氧化活性。     

制备条件对Au/LaCoO_3催化氧化CO性能的影响

采用溶胶-凝胶法制备了钙钛矿型复合氧化物LaCoO_3, 并用沉积-沉淀法(DP法)制备了Au/LaCoO_3催化剂. 考察了制备条件对催化剂催化氧化CO活性的影响. 结果表明, 制备过程中, 溶液pH、 pH调节顺序及催化剂焙烧温度对催化剂活性均有一定影响. Au/LaCoO_3催化剂的最佳制备条件为: 沉积过程中在HAuCl4溶液中先加入载体后, 再调节溶液pH=8, 得到的催化剂经250 ℃焙烧后可提高催化剂稳定性.     

Pd／MgO／γ—Al2O3的结构和催化性能的研究

用常规浸渍法和双浸渍法制备了系列ＭｇＯ／γ－Ａｌ２Ｏ３复合氧化物载体负载的钯催化剂，实验结果发现，两种制备方法所得催化剂中，钯在复合载体上沉积的部位不同，从而导致不同的色情民载体的相互作用，使得活性金属钯的电子密度发生不同程度的变化，钯催化剂对ＣＯ氧化反应活性不仅与钯分散度有关，而且催化剂中活泼的晶格氧及钯与载体作用方式有关，钯催化剂随载体ＭｇＯ含量的变化而呈现的活性变化趋势是以上各因素协同作用的     

Nafion修饰Ag/AgCl参比电极的研制及其在pH电化学传感器中的应用

制备了Nafion修饰的Ag/AgCl参比电极,参比电极电位(25℃)为-47.5±1mV,制备的电极有良好的重现性,电极电位不受溶液pH值和Cl-浓度变化的影响,有良好的抗S2-I、-离子干扰能力,且有较好的抗脉冲电流干扰能力。该参比电极适用于间歇式测试场合,可以保证稳定的参比电位;可用于基于W氧化物pH电极的电化学传感器,传感器的内阻为22kΩ,小于玻璃pH电极计内阻(1~10MΩ)。     

Phenomenological aspects related to the electrochemical behaviour of smooth palladium electrodes in alkaline solutions

The voltammetric behaviour of smooth palladium electrodes in 1 M NaOH is studied in the potential range related to the thermodynamic stability of water. The electrosorption of H atoms on bulk Pd appears as a reversible reaction coupled to a diffusion process which occurs within bulk Pd. The voltammetric electrodesorption of H from bulk Pd is a process under mixed control, i.e. the diffusion from the bulk and the surface oxidation of H atoms. Fast pseudocapacitive reactions are detected in the range 0.2–0.4 V associated with the adsorption of H atoms at the submonolayer level. The initial stages of Pd oxide layer formation, at ca. 0.68 V, involves two reversible stages. The Pd oxide monolayer formation is achieved at 1.25 V/RHE and is followed by the formation of a third reversible system. This system is enhanced by an excursion in the potential range of the oxygen evolution reaction. This reversible system is probably a redox system involving Pd(II)/Pd(IV) species. The voltammetric electroreduction of the Pd oxide film shows rather irreversible behaviour. Inhibition effects on the reversible adsorption of H atoms due to residual oxide species were observed as well as inhibition on loading the Pd electrode with hydrogen to form the (α + β)-PdH phase. Rotating ring-disc experiments demonstrate that Pd electrodissolution in basic solutions is much smaller than in acid solutions. However, soluble palladium species are detected, especially during the formation of the fast redox systems, in the potential range related to Pd oxide layer growth.     

Electrochemical deposition of Pd nanoparticles on indium-tin oxide electrodes and their catalytic properties for formic acid oxidation

Pd nanoparticles (NPs) were directly deposited on indium-tin oxide (ITO) electrodes by cyclic voltammetry (CV) in a bulk Pd²⁺ solution and the size of the Pd (NPs) was evaluated by SEM. The electrochemical deposition conditions of the Pd NPs were varied according to a scan rate. As the scan rate was decreased, the size of the Pd NPs increased, but the formic acid catalytic property was weakened. With regard to cycle number, with increased cycling, the size of the Pd NPs increased but the formic acid catalytic property decreased. As the conditions of electrochemical deposition were varied, the particle size and catalytic activity for formic acid were also changed.     

Influence of hydrogen electrosorption on surface oxidation of Pd and Pd-noble metal alloys

Electrochemical oxidation of freshly deposited Pd and its alloys with other noble metals (Au, Pt, Rh) was compared with the behavior of samples subjected to prior hydrogen absorption/desorption procedure. It was found that surface oxidation of hydrogen-treated Pd and Pd–Pt–Au deposits starts at lower potentials than on non-hydrided electrodes and is accompanied by a negative shift of surface oxide reduction peak. Pd and its alloys with Au, Pt and Rh after hydrogen treatment are also more resistant to electrochemical dissolution than freshly deposited samples.     

Preparation and characterization of palladium/polypyrrole-reduced graphene oxide/foamed nickel composite electrode and its electrochemical dechlorination of triclosan

In this study, a new composite electrode of palladium (Pd) nanoparticles dispersed on polypyrrole-reduced graphene oxide (PPy-rGO) loaded on foam-nickel was achieved by galvanostatic method. Characterization of structures, morphology and crystallinity of the synthesized materials were investigated by scanning electron microscopes (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The results of XPS and XRD demonstrated Pd showed primarily as Pd0. From SEM and TEM results, we had seen that Pd nanoparticles were dispersible well on the composite electrode. Raman spectroscopy was used to show the state of graphene oxide and further demonstrated that PPy and rGO had existed of on the foam Ni matrix. The data of EIS also suggested the charge transfer of the new composite electrode decreased compared to Pd/PPy/foam-Ni and PPy/foam-Ni composite electrodes. The effect of the electropolymerization potential on Pd/PPy-rGO/foam-Ni electrode for removing triclosan (TCS) was examined. It was found that the removal efficiency of TCS on the composite electrode could reach 100% at electropolymerization potential of 0.7 V and reaction time of 100 min.     

钯纳米线电极的制备及其应用于乙醇的电化学氧化研究

纳米线作为纳米科学领域中的重要一员,因其优异的光学、电学及磁学等特性引起了凝聚态物理学界、化学界以及材料科学界科学家们的极大关注,并己成为当今纳米科技研究的热点领域[1].纳米线的制备方法有多种,本文提及的模板法制备纳米线结构技术是20世纪90年代初发展起来的一种既经济又简便实用的新工艺[2].     

Pd/Pt二元合金电极的制备及氧还原性能

本文利用欠电位沉积亚单层的Cu及Pt置换取代Cu的方法, 制备了具有不同表面元素组成的Pd/Pt二元合金电极(用Pd/Ptx表示, x指欠电位沉积Cu-Pt置换取代Cu过程的次数),并对其表面元素组成、氧还原性能进行了表征. 在控制欠电位沉积Cu的下限电位恒定(0.34 V)的前提下, 表面Pt/Pd的元素组成比通过重复欠电位沉积Cu及Pt置换取代Cu的次数(1~5次)来可控地调变. 光电子能谱(XPS) 以及红外光谱实验表明,Pd/Ptx电极表层区的Pt：Pd元素组成比随着Pt沉积次数增加而增加, 对Pd/Pt4电极, 在电极表层区约2~3 nm内的Pt/Pd的原子比大约是1:4,而最表层裸露Pd原子的比例仍在20%以上。循环伏安结果显示, 随着Pt沉积次数的增加(1-5次), Pd/Ptx电极表面越不易被氧化。氧还原测试结果显示随着Pt沉积次数的增加(1~4次), Pd/Ptx二元金属电极的氧还原活性依次增加, 经过第3次沉积后其氧还原活性已优于纯Pt,而经4次以上沉积,其氧还原活性基本不变。在其它反应条件相同条件的前提下, Pd/Pt4电极上氧还原的半波电位与纯Pt相比右移约25 mV。结合本文与文献的实验结果,我们初步认为Pd/Ptx二元金属体系氧还原性能改善主要源自表层Pd原子导致其邻近的Pt原子上含氧物种吸附能的降低.     

Electrodeposited fabrication of highly ordered Pd nanowire arrays for alcohol electrooxidation

Highly ordered Pd nanowire arrays (NWAs) are prepared using a porous aluminum oxide template by pulse electrodeposition. The obtained Pd nanowire arrays with the diameter of 50 nm and length of 850 nm have been characterized by scanning electron microscopy, energy dispersive X-ray analysis, and high resolution transmission electron microscope. Meanwhile, the electrocatalytic activity of Pd NWAs electrodes for methanol and isopropanol oxidation in alkaline media is studied. It is found that the obtained nanostructures exhibit excellent catalytic activity for alcohol electrooxidation. The isopropanol oxidation shows the higher activity on Pd NWAs electrode than methanol in alkaline medium.     

镀Pd的GC电极上HCOOH的电催化氧化

在玻璃碳 (GC)基底上电沉积Pd ,应用SEM观测Pd沉积层的表面形貌 ,用循环伏安法研究了Pd/GC电极上HCOOH在HClO4溶液中的电氧化行为 .结果表明 ,Pd的电沉积条件影响电极的催化性能 .在高电流密度下制得的Pd/GC电极对HCOOH的电氧化具有比纯Pd电极更高的催化活性 .当电极表面生成PdO时 ,HCOOH被电氧化的活性很低 ,而在PdO还原后生成的Pd表面 ,HCOOH的电氧化显示极高的活性 .本文还讨论了Pd(Ⅱ )离子对HCOOH电氧化过程的影响 .     

纳米钯膜电极的制备、结构表征和特殊反应性能

用循环伏安方法制备纳米钯膜电极,运用扫描隧道显微镜和原位红外光谱等方法研究其结构和反应性能.STM图像表明,制备的纳米钯膜具有特殊的层状结构,纳米级厚度的层状晶体由直径6nm左右的Pd微晶聚集而成.发现当钯膜厚度为几个纳米时,CO的吸附表现出异常红外效应,即红外谱峰反向和红外吸收显著增强(增强因子可达42.6).纳米钯膜电极对氢的反应也具有特殊的性能,与氢向钯晶格扩散吸收过程相比较,氢吸脱附的表面过程成为主要反应.研究结果还指出,纳米钯膜电极的异常红外效应和对氢反应的特殊性能与钯膜厚度密切关联,并可归结为钯膜材料的纳米尺度效应.