PtRu/carbon nanotube nanocomposite synthesized in supercritical fluid: a novel electrocatalyst for direct methanol fuel cells

Platinum/ruthenium nanoparticles were decorated on carbon nanotubes (CNT) in supercritical carbon dioxide, and the nanocomposites were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM images show that the particles size is in the range of 5-10 nm, and XRD patterns show a face-centered cubic crystal structure. Methanol electrooxidation in 1 M sulfuric acid electrolyte containing 2 M methanol were studied onPtRu/CNT (Pt, 4.1 wt%; Ru, 2.3 wt%; molar ratio approximately Pt/Ru = 45:55) catalysts using cyclic voltammetry, linear sweep voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. All the electrochemical results show that PtRu/CNT catalysts exhibit high activity for methanol oxidation which resulted from the high surface area of carbon nanotubes and the nanostructure of platinum/ruthenium particles. Compared with Pt/CNT, the onset potential is much lower and the ratio of forward anodic peak current to reverse anodic peak current is much higher for methanol oxidation, which indicates the higher catalytic activity of PtRu/CNT. The presence of Ru with Pt accelerates the rate of methanol oxidation. The results demonstrated the feasibility of processing bimetallic catalysts in supercritical carbon dioxide for fuel cell applications.     

Chitosan‐Functionalized Carbon Nanotubes as Support for the High Dispersion of PtRu Nanoparticles and their Electrocatalytic Oxidation of Methanol

Carbon nanotubes (CNTs) were non‐covalently functionalized with chitosan (Chit) and then employed as the support for PtRu nanoparticles. The functionalization was carried out at room temperature without the use of corrosive acids, thereby preserving the integrity and the electronic conductivity of the CNTs. Transmission electron microscopy reveals that PtRu nanoparticles were highly dispersed on the surface of Chit‐functionalized CNTs (CNT‐Chit) with small particle‐size. Cyclic voltammetry studies indicated that the PtRu nanoparticle/CNT‐Chit nanohybrids have a higher electrochemical surface area, electrocatalytic performance, and stability towards methanol oxidation compared to PtRu nanoparticles supported on the pristine CNTs.     

阵列纳米管中铂:钌原子比对甲醇电催化氧化活性的影响（英文）

采用电化学沉积技术在3-氨丙基三甲基硅氧烷修饰的多孔氧化铝膜板中制备了具有不同Pt/Ru原子比的双元Pt/Ru阵列纳米管电极（NTAEs）。分别用X-射线衍射和扫描电镜表征了催化剂结构和形态。电化学结果表明：通过控制前驱沉积液的浓度可得到不同PtRu原子比的NTAEs。所制备的Pt 或 Pt/Ru合金阵列纳米电极的真实表面积大,催化活性强,有利于物质传输,对甲醇电氧化显示出显著的催化性能。实验中还系统研究了催化剂组成与CO和CH3OH电催化氧化性能的关系,发现Pt/Ru=50:50的阵列纳米管电极对CO电氧化显示出最好的催化活性;对甲醇电氧化,则Ru原子比为40%的催化剂显示最佳催化性能。     

Nanostructure PtRu/MWNTs as anode catalysts prepared in a vacuum for direct methanol oxidation

Platinum and ruthenium nanoparticles that are uniformly dispersed on multiwalled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using Pt(acac)2 and Ru(acac)3 as the metal precursors. The resulting nanocomposites were characterized by transmission electron microscopy and X-ray diffraction. The Pt, Pt45Ru55, and Ru nanoparticles had mean diameters of 3.0 +/- 0.6, 2.7 +/- 0.6, and 2.5 +/- 0.4 nm and the same mole number as their metal precursors at 500 degrees C. The electrocatalytic activity of the Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs exhibited a high level of catalytic activity for methanol oxidation as a result of the large surface area of the supporting carbon nanotubes and the wide dispersion of the Pt and Ru nanoparticles. Compared with the Pt/MWNTs, the onset potential for methanol oxidation of the PtRu/MWNTs was significantly lower, and the ratio of the forward anodic peak current to the reverse anodic peak current during methanol oxidation was somewhat higher. The Pt45Ru55/MWNTs displayed the best electrocatalytic activity of all of the carbon-nanotube-supported Pt and PtRu catalysts.     

以切短多壁碳纳米管为载体制备高活性Pt/SCNT及PtRu/SCNT燃料电池催化剂

采用乙醇为助磨剂,利用球磨的方法将5-15μm长的多壁碳纳米管切短成长度约为200nm,并且分布较为均匀的短碳纳米管(SCNT).以SCNT为载体,采用有机溶胶法制得了含铂20%(w)的Pt/SCNT及PtRu/SCNT催化剂.实验发现:对于甲醇的阳极电氧化过程,以切短碳纳米管为载体的Pt/SCNT催化剂具有比相同条件制得的Pt/CNT催化剂高得多的催化活性,前者甲醇氧化峰电流密度是后者的1.4倍,并且远远高于商品的Pt/C催化剂.同时我们发现添加了钌的PtRu/SCNT具有比不含钌的催化剂更好的活性.采用X射线衍射(XRD)、透射电镜(TEM)、比表面积分析(BET)等方法对催化剂进行表征,结果表明,切短碳纳米管的晶相结构并未改变,但Pt/SCNT和PtRu/SCNT催化剂的比表面积和电化学活性得到了显著的提高.     

Monodisperse porous LiFePO4 microspheres for a high power Li-ion battery cathode

A novel solvothermal approach combined with high-temperature calcinations was developed to synthesize on a large scale LiFePO(4) microspheres consisting of nanoplates or nanoparticles with an open three-dimensional (3D) porous microstructure. These micro/nanostructured LiFePO(4) microspheres have a high tap density and, as electrodes, show excellent rate capability and cycle stability.     

Co(OH)2-combined carbon-nanotube array electrodes for high-performance micro-electrochemical capacitors

We have investigated binder-free Co(OH)₂-combined carbon-nanotube (CNT) array electrodes using anodized aluminum oxide (AAO) templates for micro-electrochemical capacitors. It is shown that compared to the capacitors fabricated with CNT only electrodes (6.3 F/cm³ at 100 mV/s), those with the Co(OH)₂-combined CNT array electrodes produce much higher capacitance (12.74 F/cm³ at 100 mV/s) together with superior high-rate capacitance. The improved electrochemical behavior is explained in terms of high capacitance of amorphous Co(OH)₂ electrode and the use of CNT arrays as effective current collector.     

Development of stable PtRu catalyst coated with manganese dioxide for electrocatalytic oxidation of methanol

Manganese dioxide was coated on multiwall carbon nanotubes-supported PtRu particles to prepare the MnO₂/PtRu/CNT catalyst by a facile oxidation–reduction method. The prepared catalyst showed a high stability for electrocatalytic oxidation of methanol. After 2000 potential cycles, 55% activity still remained for MnO₂/PtRu/CNT catalyst, while only 30% activity remained for PtRu/CNT, which indicated that the electrochemical stability of MnO₂/PtRu/CNTs was improved significantly. MnO₂ in MnO₂/PtRu/CNTs prevented the dissolution of PtRu particles as well as the corrosion of the CNT supports, resulting in the improvement of the stability and activity.     

A strategy for the high dispersion of PtRu nanoparticles onto carbon nanotubes and their electrocatalytic oxidation of methanol

Carbon nanotubes (CNTs) were non-covalently functionalized by 1-pyrenecarboxaldehyde (PCA) via π-π stacking interactions. PCA not only acts as the reductant for the deposition of PtRu nanoparticles, but the oxidation product of PCA can also effectively anchor and stabilize the in-situ-produced PtRu?NPs on the surface of CNTs. Transmission electron microscopy demonstrates that PtRu?NPs are uniformly dispersed on the surface of CNTs with small particles sizes of about 1.7 nm. The obtained PtRu-NP/CNT composites have higher electrochemical surface areas, electrocatalytic activities, and better stability towards methanol oxidation compared to PtRu?NPs supported on pristine CNTs.     

低热固相法制备纳米MnO2/CNT超电容复合电极的循环稳定性

为了改善纳米MnO2超级电容器电极的充放电循环稳定性,以Mn(OAc)2·4H2O、NH4HCO3和碳纳米管(CNT)为原料,采用低热固相反应得到前驱体,再经焙烧和酸处理,制备了一系列CNT含量不同的纳米MnO2/CNT复合电极材料,并用X射线衍射(XRD)、透射电镜(TEM)和Brunauer-Emmett-Teller(BET)比表面积测定方法对其进行了表征.XRD分析结果表明,复合材料中的MnO2为纳米γ-MnO2.研究了复合电极在1 mol·L-1 LiOH电解质中的电化学性能,并与不含CNT的纯纳米MnO2电极进行了比较.结果表明,含CNTs为10%(w,质最分数,下同)和20%的MnO2/CNT复合电极的循环稳定性远优于纯纳米MnO2电极的循环稳定性,其中含10%CNTs的MnO2/CNT复合电极不仪具有良好的循环稳定性,而且在1000 mA·g-1高倍率充放电条件下仍具有200 F·g-1的高比电容.     

Electrocatalytic oxidation of ethylene glycol on Pt and Pt-Ru nanoparticles modified multi-walled carbon nanotubes

The synthesis and characterization of catalysts based on nanomaterials, supported on multi-walled carbon nanotubes (CNT) for ethylene glycol (EG) oxidation is investigated. Platinum (Pt) and platinum-ruthenium (Pt-Ru) nanoparticles are deposited on surface-oxidized multi-walled carbon nanotubes [Pt/CNT; Pt-Ru/CNT] by the aqueous solution reduction of the corresponding metal salts with glycerol. The electrocatalytic properties of the modified electrodes for oxidation of ethylene glycol in acidic solution have been studied by cyclic voltammetry (CV), and excellent activity is observed. This may be attributed to the small particle size of the metal nanoparticles, the efficacy of carbon nanotubes acting as good catalyst support and uniform dispersion of nanoparticles on CNT surfaces. The nature of the resulting nanoparticles decorated multiwalled carbon nanotubes are characterized by scanning electron microscopy (SEM) and transmission electron microscopic (TEM) analysis. The cyclic voltammetry response indicates that Pt-Ru/CNT catalyst displays a higher performance than Pt/CNT, which may be due to the efficiency of the nature of Ru species in Pt-Ru systems. The fabricated Pt and Pt-Ru nanoparticles decorated CNT electrodes shows better catalytic performance towards ethylene glycol oxidation than the corresponding nanoparticles decorated carbon electrodes, demonstrating that it is more promising for use in fuel cells.     

具有高活性和突出的抗中毒性能的Pt修饰Ru/C催化剂的制备和表征(英文)

采用两步浸渍-还原法制备了一种具有高Pt利用效率,高性能的Pt修饰的Ru/C催化剂(Ru@Pt/C).对于甲醇的阳极氧化反应,该催化剂的单位质量铂的催化活性分别为Pt/C、自制PtRu/C和商业JMPtRu/C催化剂的1.9、1.5和1.4倍;其电化学活性比表面积分别为Pt/C和自制PtRu/C的1.6和1.3倍.尤为重要的是该催化剂对甲醇氧化中间体具有很好的去除能力,其正向扫描的氧化峰的峰电流密度(If)与反向扫描氧化峰的峰电流密度(Ib)之比可高达2.4,为Pt/C催化剂的If/Ib的2.7倍,表明催化剂具有很好的抗甲醇氧化中间体毒化的能力.另外,Ru@Pt/C催化剂的稳定性也高于Pt/C、自制PtRu/C和商业JMPtRu/C催化剂的稳定性.采用X射线衍射(XRD)、透射电镜(TEM)和X射线光电子能谱(XPS)对催化剂进行了表征,Pt在Ru表面的包覆结构得到了印证.Ru@Pt/C的高铂利用效率、高性能和高抗毒能力使其有望成为一种理想的直接甲醇燃料电池电催化剂.     

Fe-Ni/TiO2纳米管阵列电极的制备、表征及光电催化还原五氯酚活性

采用阳极氧化法和浸渍电沉积联用法制备了不同负载量的Fe-Ni/TiO2纳米管阵列电极. 通过扫描电子显微镜(SEM)、 X射线光电子能谱(XPS)和电化学测量等手段对样品的微观形貌、 晶体结构和光电响应等特性进行分析. 考察了在0.6 V偏压下, 所制备的电极对五氯酚的光电催化还原性能. 结果表明, 适量的Fe和Ni纳米颗粒的负载, 降低了TiO2纳米管阵列光生电子-空穴对的复合几率; 浸渍电沉积5次的Fe-Ni/TiO2纳米管阵列电极光电催化还原降解五氯酚的效率为91.35%, 明显高于TiO2纳米管阵列电极.     

A TiO2/CNT coaxial structure and standing CNT array laminated photocatalyst to enhance the photolysis efficiency of TiO2

In this study a TiO2/CNT coaxial structure and standing CNT array laminated photocatalyst to enhance the photolysis efficiency of TiO2 is presented. An electrochemical bath that used a nanoporous anodic aluminum oxide membrane as the separation grating to separate two vessels with a transmembrane concentration gradient was constructed. The catalyzed photolysis efficiency was measured in terms of the photolysis-induced ion current. The experimental results demonstrate that the photolysis efficiency of TiO2 could be increased by the high electron conductibility of the standing CNT array. The experimental results also indicate that photolysis efficiency could be enhanced by increasing the height of the standing CNT array substrate; however, it degraded as the thickness of the TiO2/CNT coaxial structure and the TiO2 shell increased.     

Metal/metal sulfide functionalized single-walled carbon nanotubes: FTO-free counter electrodes for dye sensitized solar cells

The use of single-walled carbon nanotubes (CNT) thin films to replace conventional fluorine-doped tin oxide (FTO) and both FTO and platinum (Pt) as the counter electrode in dye sensitized solar cells (DSSC) requires surface modification due to high sheet resistance and charge transfer resistance. In this paper, we report a simple, solution-based method of preparing FTO-free counter electrodes based on metal (Pt) or metal sulfide (Co(8.4)S(8), Ni(3)S(2)) nanoparticles/CNT composite films to improve device performance. Based on electrochemical studies, the relative catalytic activity of the composite films was Pt > Co(8.4)S(8) > Ni(3)S(2). We achieved a maximum efficiency of 3.76% for the device with an FTO-free counter electrode (Pt/CNT). The device with an FTO- and Pt-free (CoS/CNT) counter electrode gives 3.13% efficiency.     

Flexible supercapacitors based on carbon nanotubes

This review provides an overview of recent progress towards the development of flexible supercapacitors based on macroscopic carbon nanotubes-based electrodes, including one-dimensional (1D) fibers, 2D films, and 3D foams, with a focus on electrode preparation and configuration design as well as their integration with other multifunctional devices.     

Amphiphilic block copolymer-stabilized PtRu nanoparticles highly dispersed on multi-walled carbon nanotube for methanol oxidation

We report a one-pot synthesis of amphiphilic block copolymer-stabilized PtRu nanoparticle modified multi-walled carbon nanotubes (MWCNTs) using RuCl(3)·xH(2)O and H(2)PtCl(6)·6H(2)O as ruthenium and platinum sources, and block copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) as stabilizer agent. PtRu alloyed nanoparticles with an average diameter of 4.6nm are well decorated homogeneously on the exterior surfaces of the MWCNTs. The electrochemical catalytic activity for methanol oxidation of PtRu/MWCNTs and commercial PtRu/C (E-TEK) is comparatively investigated using cyclic voltammetry and chronoamperometry. It is revealed that the PtRu nanoparticle modified MWCNT samples display an enhanced electrochemical catalytic activity than commercial PtRu/C electrode. These results show that PtRu nanoparticles may find applications to fuel cells.     

碱性介质中多孔纳米结构镍/钯-镍电极上甲醇电氧化反应(英文)

A nanostructured Ni/Pd-Ni catalyst with high activity for methanol oxidation in alkaline solution was prepared by electrodeposition followed by galvanic replacement, that is, electrodeposition of Ni-Zn on a Ni coating with subsequent replacement of the Zn by Pd at the open circuit potential in a Pd-containing alkaline solution. The surface morphology and composition of the coatings were examined by energy dispersive X-ray spectroscopy and scanning electron microscopy. The Ni/Pd-Ni coatings were porous and were composed of discrete Pd nanoparticles of about 58 nm. The electrocatalytic activity of the Ni/Pd-Ni electrodes for the oxidation of methanol was examined by cyclic voltammetry and electrochemical impedance spectroscopy. The onset potentials for methanol oxidation on Ni/Pd-Ni were 0.077 V and 0.884 V, which were lower than those for flat Pd and smooth Ni electrodes, respectively. The anodic peak current densities of these electrodes were 4.33 and 8.34 times higher than those of flat Pd (58.4 mA/cm2 vs 13.47 mA/cm2) and smooth Ni (58.4 mA/cm2 vs 7 mA/cm2). The nanostructured Ni/Pd-Ni electrode is a promising catalyst for methanol oxidation in alkaline media for fuel cell application.     

PtRu catalysts supported on heteropolyacid and chitosan functionalized carbon nanotubes for methanol oxidation reaction of fuel cells

A simple self-assembly approach has been developed to functionalize carbon nanotubes (CNTs) with chitosan (CS) and heteropolyacids (HPAs) of phosphomolybdic acid (H(3)PMo(12)O(40), HPMo) and phosphotungstic acid (H(3)PW(12)O(40), HPW). The non-covalent functionalization method, which introduces homogenous surface functional groups with no detrimental effect on graphene structures of CNTs, can be carried out at room temperature without the use of corrosive acids. The PtRu nanoparticles supported on HPAs-CS-CNTs have a uniform distribution and much smaller size as compared to those of the PtRu nanoparticles supported on conventional acid treated CNTs (PtRu/AO-CNTs). The onset and peak potentials for CO(ad) oxidation on PtRu/HPAs-CS-CNTs catalysts are more negative than those on PtRu/AO-CNTs, indicating that HPAs facilitate the electro-oxidation of CO. The PtRu/HPMo-CS-CNTs catalyst has a higher electrocatalytic activity for methanol oxidation and higher tolerance toward CO poisoning than PtRu/HPW-CS-CNTs. The better electrocatalytic enhancement of HPMo on the PtRu/HPAs-CS-CNTs catalyst is most likely related to the fact that molybdenum-containing HPAs such as HPMo have more labile terminal oxygen to provide additional active oxygen sites while accelerating the CO and methanol oxidation in a similar way to that of Ru in the PtRu binary alloy system.     

Wormholelike mesoporous carbon supported Pt Ru catalysts toward methanol electrooxidation

Wormholelike mesoporous carbons(WMCs) with three different pore diameters(D_p),namely WMC-F7(D_p=8.5nm),WMC-F30(D_p=4.4nm),and WMC-FO(D_p = 3.1nm) are prepared via a modified sol-gel process.Then PtRu nanoparticles with the particle size(d_(Pt)) of ~3.2 nm supported on WMCs are synthesized with a modified pulse microwave-assisted polyol method.It is found that the pore diameter of WMCs plays an important role in the electrochemical activity of PtRu toward alcohol electrooxidation reaction.PtRu/WMC-F7 with Dp 2d_(Pt) exhibits the largest electrochemical surface area(ESA) and the highest activity toward methanol electrooxidation.With the decrease in D_p,PtRu/WMC-F30 and PtRu/WMC-FO have much lower ESA and electrochemical activity,especially for the isopropanol electrooxidation with a larger molecular size.When D_p is more than twice d_(Pt),the mass transfer of reactants and electrolyte are easier,and thus more PtRu nanoparticles can be utilized and the catalysts activity can be enhanced.