Hollow carbon spheres with wide size distribution as anode catalyst support for direct methanol fuel cells

Hollow carbonaceous composites (HCCs) possessing sphere and hemisphere shape, which had wide size distribution between several tens of nanometers and several micrometers, were prepared through a facile hydrothermal method using glucose as carbon source with the assistance of sodium dodecyl sulfate (SDS). Pyrolysis of these hollow carbonaceous composites at 900 °C under nitrogen flow produced carbonized hollow carbon spheres (HCSs) without changing their structures. Platinum (Pt) was directly deposited on the surface of the HCSs by incipient wet method, using the NaBH₄ as the reductant. TEM, SEM, powder XRD and FT-IR were utilized to characterize all these samples. It was found that Pt nanoparticles were uniformly anchored on the outer and the inner surface of HCSs. The electrocatalytic properties of the Pt/HCS electrode for methanol oxidation have been investigated through cyclic voltammetry and chronoamperometry. The Pt/HCS electrode showed significantly higher electrocatalytic activity and more stability for methanol oxidation compared with Pt supported carbon microspheres (Pt/CMs) and commercial carbon (Pt/XC-72) electrode. The excellent performance for the Pt/HCS might be attributed to the high dispersion of platinum catalysts and the particular hollow structure of HCSs.     

Pt纳米空球壳厚的可控制备及对甲酸的电催化氧化

本文以约120nm的α-Se球为模板,抗坏血酸为还原剂,H2PtCl6为前驱体,通过改变氯铂酸的用量可控合成了不同壳厚的纳米铂空球（Pthollow）及其修饰玻碳（GC）电极（Pthollow／GC）;采用扫描电子显微镜（SEM）、高分辨透射电子显微镜（HR-TEM）、能量色散X射线（EDX）谱、X射线衍射（X-ray diffraction,XRD）谱和选区电子衍射（SAED）图等表征其形貌、组成与结构;以甲酸为探针分子,采用循环伏安和计时电流法研究了甲酸在Pthollow／GC电极上的电催化氧化行为．结果表明,所制备的Pthollow分散性好、粒径比较均匀,其多孔球壳是由多维多级的铂原子团簇所构建,呈现多晶铂的结构与性质;当RPt/Se=1．2时,所合成Pthollow。对甲酸的电催化氧化活性最高,且明显优于电沉积铂（Ptnano）修饰GC电极（Ptnano／GC）,为直接甲酸燃料电池（DFAFC）阳极材料的优化制备提供了一定的实验与理论依据,有潜在的应用推广价值．     

Pt纳米空球粒径的可控制备及其甲醇电催化氧化

利用表面活性剂十二烷基磺酸钠（SDSN）的调控合成不同粒径的硒模板和铂纳米空球（Pthollow）,并将其修饰于玻碳（GC）基底即可制得Pthollow/GC电极;采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、高分辨透射电子显微镜（HR-TEM）和X射线光电子能谱等观察表征了Pthollow样品的形貌与组成;以甲醇为探针分子,研究Pthollow/GC和电沉积铂电极（Ptnano/GC）对甲醇氧化的电催化活性. 结果表明,由铂原子簇团构筑的多孔铂纳米空球粒径均匀,分散性好;用4 μmol·L^-1 SDSN控制合成的直径为130 nm的Pthollow制备的Pthollow/GC电极对甲醇氧化的电催化活性最佳.     

Influence of tin on the oxidation of methanol on a platinum electrode

The influence of adsorbed tin and tin(IV) ions on the oxidation of methanol chemisorbed species as well as the methanol from the bulk of the solution was studied on a Pt electrode by voltammetric and radiometric methods. It was found that tin is not adsorbed as an ad-atom but rather as a divalent ion. Enhancement of the electrocatalytic oxidation of chemisorbed species derived from methanol was observed only in the potential range from 0.4 to 0.8 V. The influence of some factors on the electrocatalytic properties of platinum is discussed.     

A simple one-step preparation of high utilization AuPt nanoparticles supported on MWCNTs for methanol oxidation in alkaline medium

A simple one-step preparation of gold–platinum electrocatalysts supported on multi-walled carbon nanotubes (MWCNTs) with high utilization is reported. A low Pt loading series of bimetallic AuPt/MWCNTs catalysts were prepared by the improved ethylene glycol reduction method, and then they were compared in terms of the electrocatalytic activity for methanol oxidation using cyclic voltammetry (CV) and chronoamperometry in alkaline solutions. The structure of AuPt/MWCNTs was characterized by the transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The results showed high Pt utilization, uniform AuPt nanoparticles size and good electrocatalytic activity for methanol electro-oxidation. The effect of Au/Pt mass ratio on electrocatalytic activity was also investigated by CV and chronoamperometry. The highest peak current density, lowest onset potential and best anti-poisoning effect for methanol electro-oxidation appeared at the Au/Pt/MWCNTs mass ratio of 2:4:32.     

A Highly Efficient,Clean‐Surface,Porous Platinum Electrocatalyst and the Inhibition Effect of Surfactants on Catalytic Activity

Herein we report a gentle seedless and surfactant‐free method for the preparation of clean‐surface porous platinum nanoparticles. In terms of electrocatalytic CH₃OH oxidation, the clean‐surface porous platinum exhibited better performance than platinum nanoparticles and a commercial Pt/C catalyst. The porous nanostructures exhibited 2.26‐fold higher mass activity and 2.8‐fold greater specific activity than the Pt/C catalyst. More importantly, three typical surfactants, cetyltrimethylammonium bromide/chloride (CTAB/C), poly(vinylpyrrolidone), and sodium dodecyl sulfate, were chosen to study the inhibition effect of surfactants on electrocatalytic performance. It was observed that the surfactants led to a clear selective decrease in electrocatalytic performance. CTAB/C inhibited the catalytic activity the most due to the stronger interaction between the OH‐enriched platinum surface and the positively charged molecules. Thus, this work indicates that these clean‐surface porous platinum nanoparticles may be used as efficient catalysts for direct methanol fuel cells and provides a greater understanding of the inhibition effects of surfactants on catalytic activity.     

Physical and electrochemical characterizations of microwave-assisted polyol preparation of carbon-supported PtRu nanoparticles

PtRu nanoparticles supported on Vulcan XC-72 carbon and carbon nanotubes were prepared by a microwave-assisted polyol process. The catalysts were characterized by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). The PtRu nanoparticles, which were uniformly dispersed on carbon, were 2-6 nm in diameter. All PtRu/C catalysts prepared as such displayed the characteristic diffraction peaks of a Pt face-centered cubic structure, excepting that the 2theta values were shifted to slightly higher values. XPS analysis revealed that the catalysts contained mostly Pt(0) and Ru(0), with traces of Pt(II), Pt(IV), and Ru(IV). The electro-oxidation of methanol was studied by cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. It was found that both PtRu/C catalysts had high and more durable electrocatalytic activities for methanol oxidation than a comparative Pt/C catalyst. Preliminary data from a direct methanol fuel cell single stack test cell using the Vulcan-carbon-supported PtRu alloy as the anode catalyst showed high power density.     

High dispersion and electrocatalytic properties of platinum nanoparticles on graphitic carbon nanofibers (GCNFs)

Highly dispersed platinum nanoparticles were electrodeposited on graphitic carbon nanofibers (GCNFs) by cyclic voltammetry (CV) in 7.7 mM H2PtCl6+0.5 M HCl aqueous solutions. The graphitic carbon nanofibers (GCNFs) used in this paper were grown directly on a graphite disk by chemical vapor deposition (CVD). The micrographs and element composition of Pt/GCNFs/graphite electrode were characterized by scanning electron microscopy (SEM) and electron diffraction spectroscopy (EDS). The electrocatalytic properties of Pt/GCNFs/graphite electrode for methanol oxidation have been investigated by CV and excellent electrocatalytic activity can be observed even at very low platinum loading (md=8.79 microg cm(-2)). The highest mass activity (MA) for methanol oxidation reaches 323 Ag(-1) when Pt/GCNFs/graphite electrode was cycled at a sweep rate of 50 mVs(-1) by CV in 2 M CH3OH+1 M H2SO4 aqueous solutions. This may be attributed to the small particle size and high dispersion of platinum particles coated on GCNFs and shows good potential application in direct methanol fuel cell (DMFC). Additionally, the long-term cycling stability of platinum catalysts was also investigated.     

Synthesis of Hollow Platinum–Palladium Nanospheres with a Dendritic Shell as Efficient Electrocatalysts for Methanol Oxidation

Engineering the size, composition, and morphology of platinum‐based nanomaterials can provide a great opportunity to improve the utilization efficiency of electrocatalysts and reinforce their electrochemical performances. Herein, three‐dimensional platinum–palladium hollow nanospheres with a dendritic shell (PtPd‐HNSs) are successfully fabricated through a facile and economic route, during which SiO₂ microspheres act as the hard template for the globular cavity, whereas the triblock copolymer F127 contributes to the formation of the dendritic shell. In contrast with platinum hollow nanospheres (Pt‐HNSs) and commercial platinum on carbon (Pt/C) catalyst, the novel architecture shows a remarkable activity and durability toward the methanol oxidation reaction (MOR) owing to the coupled merits of bimetallic nanodendrites and a hollow interior. As a proof of concept, this strategy is also extended to trimetallic gold–palladium–platinum hollow nanospheres (AuPdPt‐HNSs), which paves the way towards the controlled synthesis of other bi‐ or multimetallic platinum‐based hollow electrocatalysts.     

电化学方法制备高分散Pt/CMK-3及其对甲醇电化学催化性能

采用直接电化学还原法在介孔碳(CMK-3)载体上直接电沉积高分散的铂纳米颗粒,制备CMK-3复合铂纳米颗粒电极(Pt/CMK-3)。 通过透射电子显微镜分析发现,铂纳米颗粒非常均匀的分布在CMK-3上,平均粒径约5 nm。 通过循环伏安测试,分析了催化剂不同负载铂含量时氯铂酸的利用率,在理论铂质量分数为20%时,这种方法制备的Pt/CMK-3所使用的氯铂酸的利用率最高,在1 mol/L CH3OH+0.5 mol/L H2SO4溶液中循环伏安测试电流密度达到382 A/g。 在相同实验条件下,Pt/CMK-3电极对甲醇电催化活性远高于Pt/XC-72(炭黑)电极和用常规电沉积方法制备的Pt/CMK-3电极。     

Pt-Mo电极上CO、甲醛和甲醇的电催化氧化-微分电化学质谱研究

利用微分电化学质谱（DEMS）研究了Mo修饰的Pt电极上CO、甲醛和甲醇的电催 化氧化,证实了Mo(IV)是催化活性样品,而且它只对弱吸附CO的氧化起催化作用, 对强吸附CO的氧化没有催化活性。在低于0.4 V的电位下,吸附在Pt电极上的Mo结 甲醇和甲醛的催化氧化是通过弱吸附CO的氧化路径进行的。     

Pt-Se纳米空球修饰玻碳电极上甲酸的电催化氧化

以无定形硒溶胶为模板制备了不同硒覆盖度(θSe)(θSe=0.49,0.39,0.06,0)的Pt-Se和Pt纳米空球(分别记为(Pt-Se)HN和PtHN),发展了利用亚硫酸盐彻底除去核壳纳米粒子上Se的方法.对获得的纳米空球进行了形貌和结构的表征,结果表明所制备的(Pt-Se)HN粒径均匀,分散性好,球壳呈多孔结构.以其作为电催化剂制备了(Pt-Se)HN修饰的玻碳(GC)电极((Pt-Se)HN/GC),利用常规电化学方法比较该电极与PtHN/GC和商用碳载铂(Pt/C)修饰GC(Pt/C/GC)电极对甲酸的催化氧化作用,发现对甲酸氧化的活性顺序为(Pt-Se)HN/GCPtHN/GCPt/C/GC.三种电极催化甲酸氧化的机理有所不同:前者更倾向于通过弱吸附中间体直接氧化成CO2的单途径机理进行,后两者则通过强吸附和弱吸附中间体的双途径机理进行.在一定Se覆盖度条件下,(Pt-Se)HN/GC对甲酸的氧化有助催化作用.     

Pt/十六烷基三甲基溴化铵纳米聚集体修饰玻碳电极促进析氢(英文)

A novel, cost‐effective, and simple electrocatalyst based on a Pt‐modified glassy carbon electrode (GCE), using cetyltrimethylammonium bromide (CTAB) as a cationic surfactant, is reported. Am‐phiphilic CTAB molecules were adsorbed on GCE by immersion in a CTAB solution. The positively charged hydrophilic layer, which consisted of small aggregates of average size less than 100 nm, was used for accumulation and complexation of [PtCl6]2? anions by immersing the electrode in K2PtCl6 solution. The modified electrode was characterized using scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, impedance spectroscopy, and electrochemical methods. The electrocatalytic activity of the Pt particles in the hydrogen evolution reaction (HER) was investigat‐ed. The results show that the CTAB surfactant enhances the electrocatalytic activity of the Pt parti‐cles in the HER in acidic solution.     

Electrocatalytic oxidation of methanol onto platinum particles decorated nanostructured poly (1,5-diaminonaphthalene) film

In this work, platinum particles decorated nanostructured poly (1,5-diaminonaphthalene) modified glassy carbon electrode (Pt/Nano-PDAN/MGCE) is prepared. The composite catalysts are characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical methods. The electrochemical methanol oxidation reaction is studied at the surface of this modified electrode. At same Pt loading, the Pt/Nano-PDAN/MGCE can act as higher efficient catalyst for methanol oxidation than that Pt/MGCE. Then, the influence of some parameters such as potential scan rates, switching potential, and methanol concentration on its oxidation as well as long-term stability of the modified electrode have studied by electrochemical methods. Also, ability of the modified electrode toward electrocatalytic oxidation of formaldehyde as an intermediate in methanol oxidation has been investigated.     

Oxygen‐Tolerant Electrodes with Platinum‐Loaded Covalent Triazine Frameworks for the Hydrogen Oxidation Reaction

Reducing the use of platinum (Pt) on polymer electrolyte fuel cell anodes is critical for the widespread dissemination of these energy conversion systems. Although Pt usage can be minimized by the even dispersion of isolated Pt atoms, no atomically dispersed Pt catalysts that promote hydrogen oxidation at a rate required for practical fuel cells have been reported to date. Covalent triazine frameworks with atomically dispersed Pt atoms (0.29 wt %) are described and it is demonstrated that the material has a high electrocatalytic hydrogen oxidation activity without an overpotential. Importantly, when the loading amount was increased to 2.8 wt %, the electrocatalytic hydrogen oxidation activity of the resulting electrode was comparable to that of commercial carbon supported 20 wt % Pt catalysts, and the catalytic activity for oxygen reduction was markedly reduced. Thus, Pt‐modified covalent triazine frameworks selectively catalyze hydrogen oxidation, even in the presence of dissolved oxygen, which is critical for limiting cathode degradation during the start–stop cycles of fuel cells.     

A general method for the rapid synthesis of hollow metallic or bimetallic nanoelectrocatalysts with urchinlike morphology

We have reported a facile and general method for the rapid synthesis of hollow nanostructures with urchinlike morphology. In-situ produced Ag nanoparticles can be used as sacrificial templates to rapidly synthesize diverse hollow urchinlike metallic or bimetallic (such as Au/Pt) nanostructures. It has been found that heating the solution at 100 degrees C during the galvanic replacement is very necessary for obtaining urchinlike nanostructures. Through changing the molar ratios of Ag to Pt, the wall thickness of hollow nanospheres can be easily controlled; through changing the diameter of Ag nanoparticles, the size of cavity of hollow nanospheres can be facilely controlled; through changing the morphologies of Ag nanostructures from nanoparticle to nanowire, hollow Pt nanotubes can be easily designed. This one-pot approach can be extended to synthesize other hollow nanospheres such as Pd, Pd/Pt, Au/Pd, and Au/Pt. The features of this technique are that it is facile, quick, economical, and versatile. Most importantly, the hollow bimetallic nanospheres (Au/Pt and Pd/Pt) obtained here exhibit an area of greater electrochemical activity than other Pt hollow or solid nanospheres. In addition, the approximately 6 nm hollow urchinlike Pt nanospheres can achieve a potential of up to 0.57 V for oxygen reduction, which is about 200 mV more positive than that obtained by using a approximately 6 nm Pt nanoparticle modified glassy carbon (GC) electrode. Rotating ring-disk electrode (RRDE) voltammetry demonstrates that approximately 6 nm hollow Pt nanospheres can catalyze an almost four-electron reduction of O(2) to H(2)O in air-saturated H(2)SO(4) (0.5 M). Finally, compared to the approximately 6 nm Pt nanoparticle catalyst, the approximately 6 nm hollow urchinlike Pt nanosphere catalyst exhibits a superior electrocatalytic activity toward the methanol oxidation reaction at the same Pt loadings.     

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.     

High Dispersion and Electrocatalytic Properties of Platinum on Functional Multi‐Walled Carbon Nanotubes

Platinum (Pt) nanoparticles were electrochemically dispersed on 4‐aminobenzene monolayer‐grafted multi‐walled carbon nanotubes (MWNTs) by a potential‐step method. The structure and nature of the resulting Pt‐MWNT composites were characterized by transmission electron microscopy (TEM) and X‐ray diffraction (XRD). The electrocatalytic properties of Pt‐MWNT composites for methanol oxidation have been investigated by cyclic voltammetry (CV) and high electrocatalytic activity can be observed. This may be attributed to the small particle size, high dispersion of platinum particles and the particular properties of MWNT supports. The results imply that the Pt‐MWNT composites have good potential applications in direct methanol fuel cell (DMFC). Additionally, the long‐term cycling stability of platinum catalysts was also investigated.     

Influence of substrate stiffness on cell-substrate interfacial adhesion and spreading: a mechano-chemical coupling model

Highly ordered three dimensionally macroporous carbon spheres (3DMPCS) were successfully prepared against removable colloidal silica crystal bead templates by carbonization of glucose. The unique structural characteristics of the well-developed three dimensionally interconnected macropores were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption. The 3DMPCS have uniform large pore structures with size about 250 nm. Pt nanoparticles were supported on the macroporous carbon spheres by two aqueous impregnation methods, and it was found that the 3DMPCS supported Pt exhibited high electrocatalytic activity for methanol oxidation.     

高利用率多壁碳纳米管负载金铂合金纳米粒子催化剂在碱性溶液中的甲醇电催化氧化性能研究

使用乙二醇还原法合成了一系列高利用率多壁碳纳米管负载的金铂双金属纳米粒子电催化剂,在碱性溶液中由循环伏安和计时电流法测试该AuPt催化剂对于甲醇氧化反应的电催化活性.透射电子显微镜、X射线衍射与X射线能谱观测催化剂形貌,表征催化剂结构.结果表明,金铂双金属纳米粒子均匀分散在碳纳米管上,催化剂具有良好甲醇电氧化性能.实验表明Au/Pt/MWCNTs比为10∶8∶32(bymass)时,该催化剂具有最高甲醇电氧化峰电流密度与最负起始氧化电位.