Pt微粒修饰纳米纤维聚苯胺电极对甲醇氧化电催化

以脉冲电流法制备的纳米纤维状聚苯胺(PANI)为Pt催化剂载体，用它制备了甲醇阳极氧化的催化电极Pt/（nano-fibular PANI）.研究结果表明, Pt/（nano-fibular PANI）电极对甲醇氧化具有很好的电催化活性,并有协同催化作用.在相同的Pt载量条件下， Pt/（nano-fibular PANI）电极比Pt微粒修饰的颗粒状聚苯胺电极Pt/(granular PANI)具有更好的电催化活性.此外， Pt的电沉积修饰方法同样影响Pt/（nano-fibular PANI）电极对甲醇氧化的催化活性.脉冲电流法沉积Pt形成的复合电极较循环伏安法电沉积得到的Pt复合电极具有更优异的催化活性.     

Facile electrochemical synthesis of a conducting copolymer from 5-aminoindole and EDOT and its use as Pt catalyst support for formic acid electrooxidation

5-Aminoindole and 3,4-ethylenedioxythiophene (EDOT) were copolymerized electrochemically on a carbon cloth (CC) electrode in an aqueous sulfuric acid solution. The as-prepared copolymer was characterized by cyclic voltammogram, SEM, and UV-vis and FT-IR spectra through which the electrochemical properties, structure, and composition of the as-obtained copolymer were determined. The electrochemical activity and stability of the as-formed copolymer are significantly improved in comparison with poly(5-aminoindole) due to the incorporation of EDOT units into the conjugated chain. The copolymer film-modified CC electrode was used as substrate for Pt particle deposition (denoted as Pt/copolymer/CC), and then, its catalytic activity towards formic acid electrooxidation was studied. Experimental results indicate that the catalytic activity of Pt/copolymer/CC towards formic acid electrooxidation is enhanced in comparison with that of Pt/homopolymer/CC, which can be attributed to the homogeneous distribution of Pt nanoparticles on the copolymer/CC substrate and the improved electrochemical activity of the copolymer film.     

纳米TiO2-Pt修饰电极的制备及其电催化活性

循环伏安;纳米TiO2-Pt修饰电极的制备及其电催化活性     

碳纳米管电极上原位沉积Pt纳米颗粒

 本文利用原位离子交换法制备了碳纳米管(CNTs)载铂(Pt/CNTs)电极. X射线光电子能谱分析表明, Pt通过离子交换载于电化学功能化的CNTs表面. 扫描电镜照片显示, Pt高度分散于CNTs表面. X射线衍射分析表明, Pt的粒径约为4.0 nm. 离子交换法所制Pt/CNTs电极的电化学表面积和Pt的利用率均大于传统Pt/CNTs电极(Pt粒径约为2.5 nm), 其对氧还原的催化活性高于传统电极. 这归因于离子交换法所制电极的特殊结构,即Pt普遍载于电化学活性位上.     

基于内嵌钴/氮掺杂多孔碳三维石墨烯笼的抗团聚高效氧还原电催化剂

氧还原反应是决定燃料电池、金属-空气电池等多种新型清洁能源存储与转化技术之性能与应用的关键反应. 铂及其合金是目前催化活性最好的氧还原反应催化剂,但其高昂的成本限制了规模化应用. 在小尺寸效应作用下,微纳米结构催化剂颗粒在电极制备与电化学反应过程中的团聚限制了催化剂本征催化活性的充分发挥. 本文基于喷雾热解技术,发展了一种基于内嵌钴/氮掺杂多孔碳三维石墨烯笼的高活性、抗团聚非贵金属氧还原反应催化剂. 此结构中,金属有机骨架化合物ZIF-67衍生的钴/氮掺杂多孔碳纳米结构是催化氧还原反应的活性中心,包覆其外的三维石墨烯笼不仅可在钴/氮掺杂碳纳米结构之间构建连续的三维载流子传导网络,且可高效抑制其在催化剂制备与电化学反应过程中的团聚与活性损失. 在碱性电解液中,此类非贵金属催化剂表现出可与铂基催化剂媲美的氧还原反应活性和优异的稳定性.     

Influence of ultrathin poly-(3,4-ethylenedioxythiophene) (PEDOT) film supports on the electrodeposition and electrocatalytic activity of discrete platinum nanoparticles

Coating a carbon electrode surface, specifically highly oriented pyrolytic graphite (HOPG) with an ultrathin film of poly-(3,4-ethylenedioxythiophene), PEDOT, provides a support on which a high density of uniformly dispersed Pt nanoparticles (NPs) can readily be formed by electrodeposition. The NPs tend to be much smaller, have a higher surface coverage, better dispersion and show a much lower tendency to aggregate, than Pt NPs produced under identical electrochemical conditions on HOPG alone. The electrocatalytic activity of the NPs was investigated for methanol (MeOH) and formic acid (HCOOH) oxidation. Significantly, for similarly prepared particles, Pt NP-PEDOT arrays exhibited higher catalytic activity (in terms of current density, based on the Pt area), towards MeOH oxidation, by an order of magnitude, and towards HCOOH oxidation at high potentials, than Pt NPs supported on native HOPG. These findings can be rationalised in terms of the enhanced oxidation of adsorbed CO, a key reaction intermediate and a catalyst poison. This research provides strong evidence that employing conducting polymers, such as PEDOT, as a support substrate, can greatly improve particular catalytic reactions, allowing for better catalyst utilisation in fuel cell technology.     

Influence of lanthanum on morphology and electrochemical performance of nano-platinum-based catalytic membrane electrode

The current research of platinum (Pt)–based catalysts focuses on reducing Pt loading in the catalysts while enhancing the catalytic activity. As a rare-earth element, lanthanum (La) has demonstrated good synergistic effect with Pt-based catalysts, because of its catalytic promoting capability and high dispersibility. Here, we fabricated La-doped nano-Pt-based catalytic membrane electrode using ion beam sputtering method. The effect of La on the morphology and electrochemical performance of the catalytic membrane electrode was investigated by scanning electron microscope, X-ray photoelectron spectroscopy, and electrochemical measurements. Compared with pure Pt-based sample, the electrochemical activity specific area of the La-doped sample increases by 74.59%, with 63.95% increase in exchange current density. The results also show that La₂O₃ enhances oxygen enrichment of the membrane electrode and reduces interfacial energy among Pt grains while pinning the grain boundaries. In addition, the inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurement shows that the Pt loading in the membrane electrodes is below 0.1 mg/cm². Thus, enhanced catalytic performance is achieved in catalysts with lower Pt loading.     

Characterization of stainless steel electrode modified by a thin film of polyaniline containing pt particles and its electrocatalytic activity for methanol oxidation

The catalytic behavior of stainless steel (SS) electrode modified by a thin film of polyaniline (PANI) containing platinum particles was studied for electrooxidation of methanol and compared with a platinated Pt/PANI electrode in acidic aqueous solution. Cyclic voltammetry (CV), chronoamperometry, CO stripping techniques were used to investigate electrochemical properties and electrocatalytic activity of SS/PANI/Pt and Pt/PANI/Pt electrodes. The morphology and particle size of Pt catalysts were characterized by Transmission Electron Microscopy (TEM) measurement. The effects of various parameters such as thickness of polymer film, medium temperature and stability of the modified electrodes on methanol oxidation were also investigated. The results indicated that the modified SS electrode exhibited a considerably high electrocatalytic activity on the methanol oxidation as well as the modified Pt electrode.     

Promoting performance and CO tolerance of Pt nanocatalyst for direct methanol fuel cells by supporting on high-surface-area silicon carbide

SiC-supported Pt nanocatalyst was prepared by electrodeposition of Pt nanoparticles on the surface of high-surface-area SiC, which was fabricated by a versatile carbothermal reduction method. Characterization studies show that such synthesis protocol leads to well distribution of Pt nanoparticles, with a mean particle size of 2.9 nm on the support. This catalyst has been electrochemically characterized toward methanol oxidation, which exhibits higher catalytic activity, durability, and electrochemical active surface area than the electrodeposited Pt on multiwalled carbon nanotubes (MWCNTs). Further investigation reveals that the SiC-supported Pt also shows superior CO tolerance to Pt/MWCNTs. These results suggest that high-surface-area SiC could be a promising supporting material for constructing high-performance methanol oxidation electrocatalysts.     

Influence of ultrathin poly-(3,4-ethylenedioxythiophene) (PEDOT) film supports on the electrodeposition and electrocatalytic activity of discrete platinum nanoparticles

Coating a carbon electrode surface, specifically highly oriented pyrolytic graphite (HOPG) with an ultrathin film of poly-(3,4-ethylenedioxythiophene), PEDOT, provides a support on which a high density of uniformly dispersed Pt nanoparticles (NPs) can readily be formed by electrodeposition. The NPs tend to be much smaller, have a higher surface coverage, better dispersion and show a much lower tendency to aggregate, than Pt NPs produced under identical electrochemical conditions on HOPG alone. The electrocatalytic activity of the NPs was investigated for methanol (MeOH) and formic acid (HCOOH) oxidation. Significantly, for similarly prepared particles, Pt NP-PEDOT arrays exhibited higher catalytic activity (in terms of current density, based on the Pt area), towards MeOH oxidation, by an order of magnitude, and towards HCOOH oxidation at high potentials, than Pt NPs supported on native HOPG. These findings can be rationalised in terms of the enhanced oxidation of adsorbed CO, a key reaction intermediate and a catalyst poison. This research provides strong evidence that employing conducting polymers, such as PEDOT, as a support substrate, can greatly improve particular catalytic reactions, allowing for better catalyst utilisation in fuel cell technology.

     

Confocal microprobe Raman spectroscopic study of the electrochemical reduction of benzene on platinum and rhodium electrodes

The dependence of the electrochemical reduction behavior of benzene on Pt and Rh electrodes on the acidity of electrolyte and the electrode potential has been studied by confocal microprobe Raman spectroscopy and electrochemical methods. The results show that benzene can be reduced directly to cyclohexane. The process is found to be significantly influenced by the acidity of the solution, the roughness of the electrode and the entity of the substrates. The catalytic efficiency of Rh electrode was found to be higher than that of Pt electrode.     

Active Junctions to Improve Sensitivity and Detection Limit of a Microdevice Based on Coulometry Coupled with Silver Metallization

For achieving miniaturization and coupling with microfluidics, electrochemical devices are advantageous. In particular, coulometry is an effective tool to analyze components in solutions of very small volumes. The sensitivity and detection limit of coulometry can be improved remarkably by converting an analyte into Ag on the same Pt electrode separated in two flow channels and measuring the amount of Ag using coulometry. We demonstrate that the cathodic and anodic potentials of both parts of the Pt electrode can be shifted and reactions can be accelerated by replacing the liquid junction connecting the two flow channels by a metal wire with redox active ends. This in turn improves the sensitivity and detection limit of the device. This effect can also be observed by directly applying a voltage to the solutions in the flow channels. The achieved detection limit for hydrogen peroxide (H₂O₂) was 2.4 nM.     

离子交换-电沉积法制备高Pt利用率多孔电极

采用离子交换-电沉积的方法(Ion-exchange/electrodeposition,IEE)制备了一种高Pt利用率催化电极,对所制备电极的表面形貌、催化活性及单电池性能用线性扫描伏安(LSV)、扫描电镜(SEM)、透射电镜(TEM)和单电池测试进行了表征. 结果表明,通过电极制备工艺和离子交换-电沉积参数的调控,能够消除碳载体表面官能团的影响,使铂阳离子只与全氟磺酸树脂(Nafion)上的H⁺进行交换. 在无铂离子的电解质中,将被交换的铂阳离子还原到与Nafion接触的碳载体上,使每一个铂纳米粒子都处于气体多孔电极的三相界面上,有效地调控铂纳米粒子的尺寸和分散度. 单电池测试表明,以铂载量为0.014 mgPt•cm^-2的IEE电极组装的电池的输出功率与铂载量为0.3 mgPt•cm-²的Nafion粘接Pt/C电极相当.     

Molten-Salt Media Synthesis of N-Doped Carbon Tubes Containing Encapsulated Co Nanoparticles as a Bifunctional Air Cathode for Zinc-Air Batteries

Cost efficient bifunctional air cathodes possessing high electrocatalytic activity are of great importance for the development of secondary Zn-air batteries. In this work, cobalt nanoparticles are encapsulated within a 3D N-doped open network of carbon tubes (Co@N-CNTs) by a molten-salt synthesis procedure conducted at a high temperature. Physical characterization demonstrates that Co@N-CNTs are comprised of Co particle inserted carbon tubes with mesoporous tube walls, providing significant active surface area for electrochemical reactions. High electrocatalytic activity of Co@N-CNTs towards both oxygen evolution and oxygen reduction reactions is due to its well-developed active surface and a synergistic effect between N-doped carbon and Co nanoparticles. Both primary and secondary Zn-air battery cells assembled using Co@N-CNTs as an air cathode show higher electrochemical performance than similar cells containing commercial Pt/C and Pt/C +RuO₂, making the newly developed material a promising alternative to existing metal-based air cathodes.     

Nano-architecture platinum catalyst layer prepared by electrophoresis deposition for PEM fuel cells

A Pt-loaded carbon black electrode was prepared by pulsed electrophoresis deposition in a Pt colloid solution as a plating bath to overcome the growth problem of a Pt catalyst during deposition in an electrochemical process. This method is a promising technique for preparing Pt catalyst layers at the polymer electrolyte/electrode interface. The particle size of the Pt catalyst loaded by electrophoresis deposition was the same as that of Pt nanoparticles (3–4 nm) in a colloid and the particle size was maintained even during deposition. The loading of the Pt catalyst was controlled by the pH of the Pt colloid and deposition time. The Pt nanoparticles were deposited on a carbon black electrode to a depth of 2.5 μm.     

基于新球型微观结构模型模拟PEMFC催化层

建立了一个新球型催化层微观结构模型, 并基于此模型对质子交换膜燃料电池(PEMFC)性能进行了模拟. 该模型中假设催化层由Pt/C 颗粒和离子聚合物-孔混合相组成. 假设Pt/C 颗粒为球形结构, 其直径符合正态分布, 用不同直径的球来表示随机分散在电极中的Pt/C 颗粒. 计算了催化层内的传递和电化学反应, 研究了质子和氧气及电化学反应速率在电极厚度方向上的分布, 并且通过对比氧气浓度、过电位和电化学反应速率的分布、极化曲线及催化剂利用率等证明了适当的电极厚度与Pt/C颗粒粒径有利于提高电池性能.     

Electrochemical impedance analysis of methanol oxidation on carbon nanotube-supported Pt and Pt-Ru nanoparticles

Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) are employed to investigate methanol oxidation reactions on single-walled carbon nanotube-supported platinum (Pt) and platinum–ruthenium (Pt-Ru) nanoparticles. EIS and CV measurements show consistent results: Pt catalyst supported on single-walled carbon nanotubes possesses higher catalytic activity for methanol oxidation than that on carbon black. Additionally, semicircles in the second quadrant of the Nyquist diagrams are observed for methanol oxidation on all types of catalytic nanoparticles when applying an electrical potential of 600 mV, which indicates the occurrence of negative resistance during electrocatalytic methanol oxidations. However, all impedance spectra show positive resistance at other electrode potentials (e.g., 300, 400, and 800 mV). Electrocatalytic characteristics of all catalysts are further analyzed by equivalent circuit simulations. We propose that intermediate coverage on the catalyst surface and subsequently the oscillation of nonlinear electrochemical methanol oxidations lead to the occurrence of negative resistance at 600 mV.     

Pt/SPE电极的制备及其电化学性能

固态电解质;Pt/SPE电极的制备及其电化学性能     

碳纳米管负载纳米铂修饰电极及电催化氧化H2O2的研究

采用化学气相沉积法在碳纳米管(CNT)上负载Pt纳米颗粒,并制备了CNT-Pt修饰玻碳电极(CNT-Pt/GCE).研究了该修饰电极在磷酸缓冲液中对H2O2的电催化氧化作用以及实验条件的影响.计算了H2O2在CNT-Pt/GCE上的电极反应速率常数.结果表明,CNT-Pt/GCE对H2O2的电化学氧化具有良好的催化作用,电极反应速率常数比铂电极高约2.65倍.初步探讨了电催化氧化机理,为酶电化学传感器的研制提供了一条新的途径.     

Pt/WO_3/C nanocomposite with parallel WO_3 nanorods as cathode catalyst for proton exchange membrane fuel cells

Pt/WO3/C nanocomposites with parallel WO3 nanorods were synthesized and applied as the cathode catalyst for proton exchange membrane fuel cells(PEMFCs). Electrochemical results and single cell tests show that an enhanced activity for the oxygen reduction reaction(ORR) is obtained for the Pt/WO3/C catalyst compared with Pt/C. The higher catalytic activity might be ascribed to the improved Pt dispersion with smaller particle sizes. The Pt/WO3/C catalyst also exhibits a good electrochemical stability under potential cycling. Thus, the Pt/WO3/C catalyst can be used as a potential PEMFC cathode catalyst.