炭气凝胶负载PtRu纳米颗粒用作甲醇氧化催化剂

采用乙二醇还原法制备了以炭气凝胶(CA)为载体的PtRu纳米颗粒催化剂.透射电镜(TEM)观察得知:PtRu的粒径为3nm左右,且在载体CA表面均匀分散.循环伏安和恒电位测试表明:催化剂的甲醇氧化启动电位和载体的孔结构没有明显依赖关系.以平均孔径较大的炭气凝胶为载体制备的催化剂拥有较高的甲醇氧化催化活性.可以认为催化剂活性的差异主要是由其不同的传质性能决定的.甲醇在较大的孔中扩散比较快,更容易到达PtRu颗粒的表面,从而提高了贵金属Pt的利用效率.     

Pt nanowire electrodes electrodeposited in PVP for methanol electrooxidation

We report Pt nanowire electrodes fabricated by means of electrodeposition method as a function of molecular weight of polyvinylpyrrolidone (PVP-L and PVP-H). The higher molecular weight of PVP results in a smaller grain size of Pt nanophases in the electrode. The Pt nanowire array electrode electrodeposited with PVP-H shows the smallest gain size of Pt and an excellent catalytic activity for methanol electrooxidation in comparison with pure Pt nanowire array electrodes electrodeposited without PVP and with PVP-L.     

多壁碳纳米管改性铂型IPMC的试验研究

将一种全氟磺酸树脂(Nafion)与多壁碳纳米管(MWCNTs)分别按质量比100:1、 100:3、 100:5进行配比, 采用溶剂浇铸法配合超声波分散法制备MWCNTs/Nafion型离子交换膜(IEM), 在此基础上利用化学沉积法制备铂型离子聚合物金属复合材料(Pt-IPMC), 考察三种MWCNTs负载量对IEM及Pt-IPMC性能的影响。采用SEM配合EDAX研究Pt的沉积效果, 对IEM及Pt-IPMC试样进行拉伸测试, 采用数字信号发生器为激励源测试Pt-IPMC的动态位移。结果表明: 添加MWCNTs使Pt-IPMC的内、 外电极厚度分别增加200%~250%和180%~200%, 使IEM及Pt-IPMC的弹性模量分别提高57.92%~140.85%和9.06%~52.85%; MWCNTs有效修饰了Pt-IPMC的内电极, 并明显提升其动态位移量、 动态响应及变形速度。     

Ascorbate electro-oxidation by modified electrodes: Polypyrrole and polypyrrole/Ni(OH)2 composite thin films

The present paper describes the utilization of polypyrrole and the composite of polypyrrole doped with nickel hydroxide modified electrodes toward the catalytic oxidation of ascorbate. Films were potentiostatically deposited onto a glassy carbon surface and Fluor-doped tin oxide glass for different times. The physical characterization was performed using the low angle X-ray diffraction technique. Furthermore, the films were electrochemically characterized using cyclic voltammetry. The X-ray diffraction results show the existence of different polymorphic phases of nickel hydroxide in the polymer matrix, and the β-Ni(OH)₂ phase appears to be dominant. The cyclic voltammetry profile in KOH solution shows the presence of two redox peaks that are related to the Ni^II/Ni^III and Ni^III/Ni^II couples, at approximately 0.5 and 0.35 V, respectively. The reversible electro-oxidation of ascorbate was observed on the surface of the polypyrrole and composite films. The analytical curves obtained using voltammetric techniques show a linear relationship between the faradaic current and the increase of the ascorbic acid concentration. The sensitivity of these films, which is obtained from the slope of the analytical curves, shows that the composite film is more electroactive than the polypyrrole film: 133.4 mA L mol^− 1 cm^− 2 and 83.8 mA L mol^− 1 cm^− 2, respectively. The rate constants of the catalytic ascorbate electro-oxidation were also reported, where the mean values were found to be 217.74 M^− 1 s^− 1 and 54.37 M^− 1 s^− 1, for the composite and polypyrrole films, respectively. The low cost of polypyrrole doped with Ni(OH)₂ composite electrodes presents a more selective and high sensitivity to determine ascorbic acid concentration.     

Progress in modified carbon support materials for Pt and Pt-alloy cathode catalysts in polymer electrolyte membrane fuel cells

H₂-fed polymer electrolyte membrane fuel cells (PEMFCs) are the most advanced fuel cell technology to date and continue to be of great interest as prospective energy sources in numerous applications, including for low/zero-emission electric vehicles, distributed power generators in homes, and small portable electronic devices. However, the commercialization of PEMFC technology has been greatly hindered by certain challenges, mainly the sluggish kinetics of the oxygen reduction reaction at the cathode and the high cost of Pt-based cathode catalysts, the latter presently accounting for over 55% of the total PEMFC cost. To overcome the limited stability of state-of-the-art Pt/C, Pt and Pt-alloy catalysts supported on modified carbon materials have garnered significant interest in recent years. It is therefore timely to compile a review that focuses on Pt and Pt-alloy catalysts supported on modified carbon materials, examining their current R&D status, applications, challenges, and future prospects. This review provides a systematic and comprehensive survey of current Pt and Pt-alloy PEMFC cathode catalysts in terms of materials selection and design, synthesis methods, and structural features, emphasizing how these various aspects relate to the catalysts’ physicochemical characterization and performance, and with the aim of shedding light on the future direction of PEMFC research.     

Simple preparation of tungsten carbide supported on carbon for use as a catalyst support in a methanol electro-oxidation

Two types of supported tungsten carbides were prepared via the impregnation of tungsten precursors on carbon support followed by heat treatment. Depending on whether ammonium metatungstate (AMT) or tungsten chloride (WCl₆) was used as the precursor, this process resulted in samples that are referred to as either WC-A or WC-W, respectively. Both WC-A and WC-W showed tungsten subcarbide (W₂C) as the major crystalline phase, with tungsten monocarbide (WC) as a minor phase. More amount of tungsten carbide being formed when WCl₆ was used as the precursor. This increased formation has occurred because the thermodynamically favorable properties of WCl₆ caused the contact area between the tungsten precursor and the carbon support to promote formation of tungsten carbide. The prepared tungsten carbides were used as a catalyst support of the Pt catalyst in a methanol electro-oxidation. The metal dispersion and the catalytic performance were increased as follows: Pt/C<Pt/WC-A<Pt/WC-W. It is believed that the tungsten carbides supported on the carbon support improved the dispersion of Pt and the activation of water for removal of intermediate CO, which enhanced the catalytic performance during the methanol electro-oxidation.     

Nonionic surfactant-templated mesoporous carbon as an electrocatalyst support for methanol oxidation

Two carbons were synthesized for use as platinum electrocatalyst supports for methanol oxidation. For both materials, furfuryl alcohol was used as the carbon precursor; however, one (CPEG) was made using poly ethylene glycol as the pore former, while the other (CSRF) was produced using Pluronic^® F127 as the soft template by organic–organic self-assembly. The CPEG and CSRF carbons were estimated from nitrogen physisorption experiments to be micro- and mesoporous, respectively. Platinum nanoparticles were deposited on each carbon as well as on Vulcan XC-72 carbon by the formic acid reduction method. The physicochemical properties of electrocatalysts were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX), and their electrochemical features were examined using cyclic voltammetry, chronoamperometry, and impedance spectroscopy. It was found that higher methanol oxidation peak current densities as well as lesser charge transfer resistance at electrode/electrolyte interface were obtained for Pt supported on CSRF as compared to those on Vulcan XC-72 carbon, owing to the higher specific surface area and larger total pore volume (696 m² g⁻¹ and 0.60 cm³ g⁻¹, respectively) together with superior electrical conductivity of mesoporous CSRF. On the other hand, the lower surface area and pore volume of microporous CPEG substrate confined Pt nanoparticles deposition and thus made CPEG-supported Pt an inefficient methanol oxidation electrocatalyst.     

Highly conductive polymer materials based multi-walled carbon nanotubes as counter electrodes for dye-sensitized solar cells

Poly(3,4-ethylenedioxxythiophene) (PEDOT), polyaniline (PANI) and polythiophene (PTh) based multi-walled carbon nanotube (MWCNT) composites were successfully prepared using RF-rotating plasma grafting method. Morphological characterizations of composites were determined using scanning electron microscopy (SEM), which showed that conducting polymers (CPs) of PEDOT, PANI and PTh were coated on the surface of CNTs. The surface properties of the Carbon Nanotube (CNT) composites were also determined by using Infrared Spectra (FT-IR), X-ray Photon Spectra (XPS), and Scanning Electron Microscopy-Energy Dispersive X-ray Spectra (SEM-EDX) analysis. X-ray photon spectra results confirmed the formation of the composites. Composites of MWCNT were used in dye-sensitized solar cells (DSSCs) as counter electrodes and exhibited short-circuit photocurrent densities of 11.19, 10.70 and 8.54 mA/cm² for PANI/MWCNT, PTh/MWCNT and PEDOT/CNT, respectively.     

Preparation of Pt/multiwalled carbon nanotubes modified Au electrodes via Pt–Cu co-electrodeposition/Cu stripping protocol for high-performance electrocatalytic oxidation of methanol

Pt nanoparticles well dispersed on multiwalled carbon nanotubes (MWCNTs) were prepared for high-performance electrocatalytic oxidation of methanol in both acidic and alkaline media via the co-electrodeposition/stripping (CS) protocol, namely, co-electrodeposition of Pt and Cu followed by electrochemical stripping of Cu, as examined by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The Pt catalyst prepared by the CS protocol on MWCNTs (Pt_cs/MWCNTs/Au) exhibited a specific electrocatalytic activity of 519 and 2210 A g⁻¹ toward cyclic voltammetric electrooxidation (50 mV s⁻¹) of methanol in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH media, respectively, which are larger than those prepared by conventional electrodeposition from chloroplatinic acid on Au and MWCNTs/Au, as well as that by a CS protocol on Au. The Pt_cs/MWCNTs/Au electrode also possessed the highest stability, which maintained 91% and 90% of its initial catalytic activity after 120-cycle CV in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH, respectively. The electrode kinetics of methanol oxidation is also briefly discussed. The nanosubstrate-based CS protocol is simple, convenient and efficient, which is expected to find wide applications in film electrochemistry and electrocatalysis.     

Fe(CN)6 incorporation on Poly(3,4-ethylenedioxythiophene) films: Preparation and X-ray Photoelectron Spectroscopy characterization of the modified electrodes

Poly(3,4-ethylenedioxythiophene) (PEDOTh) films were potentiodynamically deposited on platinum from tetrabutylammonium hexafluorophosphate/acetonitrile solutions. Polymers prepared with different number of cycles showed reversible redox behaviour and the X-ray Photoelectron Spectroscopy (XPS) characterization revealed the existence of zones with different conductivity and confirmed the presence of PF₆⁻. The incorporation of the metallic complex Fe(CN)₆³⁻ in the PEDOTh films was made in one step, after the electrosynthesis of a film grown with a given number of potential cycles, and by means of polymerization/incorporation sequences. XPS data confirmed the presence of the inorganic species and the highest Fe 2p_3/2 peak intensity was observed for thin films (30 cycles) when the one step incorporation has been used. The XPS results suggest a partial dissociation of the Fe-(C-N) bond of the complex in the modified electrodes.     

羟基锡酸盐载铂复合催化剂Pt/(Co,Zn)Sn(OH)6的合成及其甲醇电催化氧化性能

以羟基锡酸盐CoSn（OH）₆和ZnSn（OH）₆纳米空心立方体为前体,采用抗坏血酸作为弱还原剂,经过超声过程分别合成了羟基锡酸钴载Pt/CoSn（OH）₆和羟基锡酸锌载Pt/ZnSn（OH）₆复合催化剂,并在甲醇氧化反应（MOR）中表现出良好的性能。Pt/CoSn（OH）₆和Pt/ZnSn（OH）₆催化剂的单位质量活性分别为1 095.6 mA/mg和699.5 mA/mg,高于C载Pt（Pt/C）的594.6 mA/mg。利用XRD、SEM、TEM、XPS和电化学测试对催化剂晶体结构和性能间的关系进行了探索。CO溶出实验结果表明,羟基锡酸盐载体有利于Pt表面CO的去除,载体与Pt间的强相互作用和载体表面的大量羟基基团增强了催化剂的催化活性和CO抗毒性。此外,Pt/（Co,Zn）Sn（OH）₆催化剂中单质Pt高的相对含量也有利于提高MOR活性。通过研究载铂羟基锡酸盐电催化氧化甲醇性能,能够揭示载体结构对催化性能的影响,有助于羟基锡酸盐载铂复合催化剂在直接甲醇燃料电池（DMFCs）领域的应用。     

炭气凝胶负载Pt基催化剂的制备及其甲醇氧化催化性能

以间苯二酚(R)和甲醛(F)为原料,制备R-F炭气凝胶(RF-CAs).继以后者为载体采用浸渍还原法制备铂基催化剂Pt/CA,并比较其与由相同负载工艺制得的以Vulcan XC-72为载体的铂基催化剂Pt/XC72的催化甲醇氧化反应的性能.结果表明,前者具明显高的甲醇氧化催化活性,显示CAs是一种极具潜在竞争力的燃料电池催化剂载体材料.     

Facile and selective approach towards synthesis of a series ZSM-5/ZSM-12 catalysts for methanol to hydrocarbons reactions: Applying different synthesis driving force and conditions

The use of ultrasonic waves was developed for synthesis of zeolites at shorter crystallization time with improving their desirable properties. A series of nanostructured ZSM-5/ZSM-12 composite zeolites with different Si/Al ratios and alkalinity using organic templates were prepared by hydrothermal and sonochemical synthesis methods. The physicochemical properties of synthesized nanocatalysts such as structure, morphology, textural, and acidity were characterized via XRD, FESEM, N₂ physisorption, FTIR, TPD-NH₃, TGA-DTG techniques. The results revealed that increasing the Si/Al ratio and alkalinity in the hydrothermal samples enhanced the crystallization, formation of amorphous microcrystals, and dominant phase of MFI with decreasing MTW competitive phase. Zeolites synthesized by high-temperature and short-time sonochemical method had higher crystallinity, less dominant phase of ZSM-5, smaller crystals, greater surface areas, higher concentration of Brønsted acid sites, and stronger strength of moderate/strong acid sites. The catalytic performance of the zeolites for MTH conversion was evaluated under a reaction temperature of 450 °C at different times on stream. The results showed that the sonochemical zeolite had a higher methanol conversion (100%), higher selectivity toward olefins (28% vs. 19%) with more C₃⁼/C₂⁼ ratio (0.79 vs. 0.58), and lower alkanes selectivity (66% vs. 72%) after 240 min TOS.     

扁形钛铜复合棒挤压模具设计与应用

对长宽比较大的扁形截面钛铜复合棒的挤压模具进行了设计研究。通过合理选材,并选择使挤压力最小的模具模腔轮廓曲线和半模角,改变模孔工作带的几何形状与尺寸,选择适当的挤压速度等,优化设计制备出扁形钛铜复合棒专用挤压模具。增加工作带长度可以增大摩擦阻力,使向该处流动的供应体的流动静压力增大,迫使金属向阻力小的方向流动,从而使型材整个断面上金属流量更加均匀。挤压实验结果表明,合理的模具设计对挤压材的挤压过程和挤压制品质量有重要影响,锥形模具更适合于扁形钛铜复合棒的挤压。解决了科研生产实际对大的长宽比扁型钛铜复合棒的需求。     

沿[111]方向择优生长Pt/Ti电极制备及析氯电催化活性

针对目前低浓度氯化钠电解过程中存在的氧化物尺寸稳定阳极(DSA)使用寿命短以及Pt电极使用量高的问题, 本研究通过磁控溅射法制备了具有沿[111]方向择优生长的Pt/Ti电极。SEM结果显示, 磁控Pt表面平整, 分散均匀, 粒度大小为10 nm; 通过XPS表征, 未见到基体Ti的特征峰, 说明其表面覆盖度好。电化学循环伏安曲线(CV)显示, 磁控Pt的电化学面积最小, 仅为1.08 cm², 接近电极表观面积; 磁控Pt氧区吸附电量和氢区吸附电量的比仅为0.83, 说明其对氧吸附能力较差, 不利于发生析氧反应。在单位电化学面积上, 当电极电势为1.6 V时, 磁控Pt的析氯电流达到0.085 A/cm², 分别是电沉积Pt和热分解Pt的3.27和49.0倍, 说明磁控Pt单位活性位点上具有很高的析氯反应活性。在此基础上, 进一步研究表明磁控Pt电极析氯反应的Tafel斜率为44.3 mV/dec, 其析氯反应机理符合Volmer-Heyrovsky机理, 速控步骤为电化学复合脱附步骤。     

超声频率对碳纳米管结构及其负载PtRu催化剂催化活性的影响

在浓硝酸和浓硫酸混合液中,采用频率分别为25、40、60和80kHz的超声波对碳纳米管(CNTs)进行官能团化处理,运用X射线衍射(XRD)、傅立叶红外(FT-IR)、热重分析(TG)等手段,考察了超声处理对碳纳米管晶相结构、表面基团、含氧基团含量的影响.以不同超声频率处理的碳纳米管作为载体,制备了一系列碳纳米管负载PtRu催化剂,并用X射线衍射技术对催化剂的晶体结构进行了表征.采用循环伏安法(CV)测试了催化剂对甲醇电氧化反应的催化活性.结果表明,采用超声频率为60Hz处理的碳纳米管具有较高的含氧基团含量,用其作为载体制备的PtRu/CNTs60催化剂具有最佳的甲醇电氧化催化活性.     

Synthesis and characterization of platinum thin film as top electrodes for multifunctional layer devices by PLD

Platinum thin films were grown onto (001) oriented SrTiO₃ substrates by means of the pulsed laser deposition technique. Structural and morphological characterizations were performed using XRD and AFM. The influence of substrate temperature and deposition rate was analyzed on the crystallographic properties of the film. As a result, an increment in the crystallinity of the film due to the change on the temperature was observed. On the other hand, Pt films showed a granular morphology and its roughness was related to the fluence and low deposition temperature. Finally their electrical properties were analyzed and discussed as a function of the previous morphological results.     

Highly dense and uniformly dispersed platinum nanoparticles on poly(acrylic acid) modified multi-walled carbon nanotubes for methanol oxidation

Poly(acrylic acid) modified multi-walled carbon nanotubes (PAA-MWNTs) were synthesized through in situ radical polymerization in acetone and the PAA-MWNTs were used as supporting material for platinum nanoparticles. Platinum nanoparticles were deposited on the surface of PAA-MWNTs with high loading and high dispersion through ethylene glycol reduction. The size of Pt nanoparticles on PAA-MWNTs can be tuned by the water content in the reaction system and the loading amount can be adjusted by the mass ratio of H₂PtCl₆ to PAA-MWNTs. The electrocatalytic properties of the Pt/PAA-MWNTs catalyst were evaluated by methanol oxidation. The results of cyclic voltammetry show that the Pt/PAA-MWNTs composite possesses high electrocatalytic activity, good long-term stability and storage property, which can be attributed to the small particle size and high dispersion of Pt nanoparticles as well as the nature of MWNTs.