碳载体的O3处理对直接甲醇燃料电池Pt-Ru/C催化剂性能的影响

为了提高直接甲醇燃料电池阳极催化剂的催化活性, 利用O₃处理的Vulcan XC-72碳黑为载体, 制备Pt-Ru/C催化剂, 并与未经处理的Vulcan XC-72为载体制备的Pt-Ru/C催化剂的性能进行比较. 采用XPS和BET测试了O₃处理后碳粉表面的含氧浓度和比表面积, 结果表明, 随处理时间延长, 碳表面含氧浓度先减少后增加, 比表面积减小; 而随着处理温度升高, 比表面积增加, 含氧浓度先减少后增加. XRD, TEM方法对催化剂的结构及形貌的表征结果表明: O₃处理的碳黑为载体制备的Pt-Ru/C催化剂粒径均匀、分散性好. 在0.5 mol/L CH₃OH和0.5 mol/L H₂SO₄溶液中, 利用粉末微电极测试了循环伏安和稳态极化曲线, 结果表明: O₃处理碳粉为载体的催化剂比未经处理的碳粉为载体的催化剂的活性高. 研究了O₃处理碳粉的时间和温度对催化剂性能的影响, 电化学测试表明: 140 ℃处理6 min的碳粉为载体制备的催化剂对甲醇的电催化氧化活性最佳.     

Carbon nanotubes as a support for Pt-and Pt-Ru-catalysts of reactions proceeding in fuel cells

Comparative study of two types of single-wall carbon nanotubes and standard carbon black Vulcan XC-72 as supports for catalysts of reactions proceeding in fuel cells is carried out. The nanotubes were prepared by arc method; they differed in the degree of their purifying from amorphous carbon and metal impurities. The structure and hydrophobic-hydrophilic properties of these carbon supports are studied by etalon porosimetry. The effect of the supports’ specific surface area on the deposited catalyst particles size and specific surface area is studied. The catalysts (Pt-Ru and Pt) were deposited from aqueous solutions of their salts. Platinum was also deposited by thermal decomposition of ethoxy clusters. It is shown that in methanol oxidation reaction at the Pt-Ru catalysts the current values per unit true surface area do not depend on the support nature, provided the catalyst loading is equal and the particle size is similar. When oxygen is reduced at platinum deposited onto purified nanotubes and the carbon black Vulcan XC-72, specific kinetic currents also are close to each other. It is shown that the degree of nanotubes purification and their structure affect the kinetics of this reaction significantly.     

The carbon nanotubes-polyaniline composites and their effect on catalytic properties of deposited catalysts

Composites of functionalized single-wall carbon nanotubes and polyaniline are deposited onto electrodes by in situ electrochemical polymerization. Their electrochemical behavior and differential capacitance are studied by cyclic voltammetry, electrochemical impedance spectroscopy, and chronovoltamperometry. The differential capacitance of the composite electrode exceeds that of pure polyaniline film deposited onto electrode, which can be explained by the nanotubes’ loosening effect on the polyaniline structure. The composite-electrode capacitance is as large as 1000 F g⁻¹ or higher. Thus obtained composite films were used as a support for deposited platinum-ruthenium catalyst. The Pt-Ru structure and catalytic properties in the methanol oxidation reaction are studied. It is shown that the specific current of methanol oxidation at Pt-Ru is larger by a factor of 7–15 than those measured when pure polyaniline, pure carbon nanotubes, or standard Vulcan XC-72 carbon black are used as supports. It is found that the catalytic activity is the same for all studied supports, provided the current is reduced to the unit of Pt-Ru true surface area. Thus, the observed large catalytic effect is associated with the structure and high dispersivity of the electrodeposited metals incorporated to the single-wall carbon nanotubes-polyaniline composite.     

Dispersed platinum supported by hydrogen molybdenum bronze-modified carbon as electrocatalyst for methanol oxidation

A new electrocatalyst, Pt/H_xMoO₃-C, for methanol oxidation, was prepared by dispersing platinum nano-particles on Vulcan XC-72 modified by hydrogen molybdenum bronze (H_xMoO₃, 0 ≤ x ≤ 2). The modification of Vulcan XC-72 with H_xMoO₃ on was accomplished by reducing the adsorbed molybdic acid and the platinum nano-particles were dispersed on the modified carbon by reducing chloroplatinic acid, with formaldehyde as the reductant. The prepared Pt/H_xMoO₃-C was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersion spectrometer, cyclic voltammetry (CV), chronoamperometry (CA), and single-cell test, with a comparison of the electrocatalyst, carbon-supported platinum (Pt/C) prepared under the same condition but without the modification. The results obtained from XRD and SEM showed that the modification of Vulcan XC-72 with H_xMoO₃ reduced the platinum particle size and improved distribution uniformity of platinum on carbon. The results, obtained from CV, CA, and the single-cell test, showed that Pt/H_xMoO₃-C exhibited better electrocatalytic activity toward methanol oxidation than Pt/C.     

Activity evaluation of carbon paste electrodes loaded with pt nanoparticles prepared in different radiolytic conditions

Three Pt-based catalysts prepared in different radiolytic conditions and supported on graphite powder were packed into a carbon paste electrode configuration. They were compared to each other, to the commercial (Pt) deposited on activated carbon powder (Johnson Matthey) and to pure Vulcan XC-72 for their respective abilities toward the hydrogen evolution reaction (HER). The Tafel parameters were determined for all these electrodes. From the I–V curves and their quantitative treatment, the following order of activity emerged unambiguously and reads: (PtCO)₂ (fcc structure) > (PtCO)₁ (Chini cluster) > (Pt)_neat > (Pt)_JM (Johnson Matthey) ≫ (Vulcan XC-72). As expected, all the Pt-loaded electrodes were more efficient than Vulcan XC-72. The classification appears to be linked with the mean nanoparticle size, and for comparable sizes, with the surface morphology of the materials. The results and the stability of the electrodes suggest that the small particle sizes and the good dispersity on the carbon support were maintained during the HER.     

Ir–V nanoparticles supported on microstructure controlled carbon nanofibers as electrocatalyst for oxygen reduction reaction

Ir–V nanoparticles supported on microstructure controlled carbon nanofibers (CNFs) or on carbon black, Vulcan XC-72 (XC-72), have been synthesized via chemical reduction, and the oxygen reduction reaction (ORR) properties of catalysts are investigated in this paper. The physico-chemical properties are characterized by high resolution transmission electron microscope (HRTEM), N₂ physisorption and electrochemical analysis. HRTEM results show that the metal nanoparticles are separated on carbon support with well-controlled particle size, dispersity, and composition uniformity. Moreover, the metal nanoparticles on CNFs have a smaller size than those on XC-72. Cyclic voltammetric analysis reveals that Ir–V/CNFs exhibits a higher ORR activity than Ir–V/XC-72, and this may be associated with the smaller metal nanoparticles and the stronger metal-support interaction of Ir–V/CNFs. Linear sweep voltammetric analysis at different rotation rates proves that ORR on the Ir–V/CNFs electrode is a 4e^? process.     

反胶束法制备直接甲醇燃料电池Pt-Sn/C催化剂及其表征

在水/AOT/环己烷反胶束体系中, 制备了Pt-Sn/C催化剂, 研究了不同ω (反胶束溶液中水与表面活性剂的物质量之比)值对Pt-Sn粒径的影响. 并采用TEM, XRD, XPS, 循环伏安等技术对其进行表征. TEM结果表明合成的Pt-Sn纳米颗粒为球形, 在碳载体表面均匀分布, 粒径分布窄, 平均粒径为2.7 nm. Pt-Sn颗粒尺寸随着ω的增加而增大. XRD结果表明该催化剂中Pt具有面心立方结构且没有与Sn形成合金. XPS结果表明在该催化剂中, Pt主要以零价态存在. 在甲醇溶液中的循环伏安扫描结果表明, 甲醇氧化峰电位和峰电流随着ω的增加而减小, 说明反胶束方法可以通过控制颗粒尺寸, 从而影响催化剂的电氧化活性. 相对于商用Pt-Ru/Vulcan XC-72 (20 wt%, E-TEK公司), 该催化剂具有较低的峰电势以及较高的I_f/I_b (循环伏安曲线中正向扫描峰电流与反向扫描峰电流的比值), 这表明用此方法制备的Pt-Sn/C催化剂具有较好的抗中毒能力.     

Controllable Electrodeposition of Platinum Nanoparticles on Graphene Nanosheet for Methanol Oxidation Reaction

A simple and cost-effective electrochemical method synthesized platinum nanoparticles on graphene nanosheet (PtNPs@GNS) is reported, and the Pt loading of the PtNPs@GNS can be controlled by electrodeposition. The structure and element analysis of the PtNPs@GNS have been investigated by scanning electron microscopy (SEM), Raman spectrum, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The electrochemical measurement including electrochemical active surface area, current density, mass activity, oxidation peak potential,shows the PtNPs@GNS have more performance electrocatalytic properties for methanol oxidation reaction (MOR) compared to Vulcan XC-72 carbon (XC-72) supported PtNPs electrocatalysts. Probably, the cause which may be attributes to no aggregation of PtNPs and the well-dispersion on surface of GNS, so PtNPs@GNS show large electrochemically active surface area, highly electrocatalytic activity and stability in direct methanol fuel cells.     

The study of the pyrolysis products of Ni (II) and Pd (II) chelate complexes as catalysts for the oxygen electroreduction reaction

Journal of Solid State Electrochemistry - Nitrogen-doped carbon materials were prepared by the pyrolysis of carbon black Vulcan XC-72 impregnated with nitrogen-containing Pd (II) and Ni (II)...     

Pt supported on carbon nanofibers as electrocatalyst for low temperature polymer electrolyte membrane fuel cells

Carbon nanofibers synthesized via the thermo catalytic decomposition of methane were investigated for the first time as an electrocatalyst support in PEMFC cathodes. Their textural and physical properties make them a highly efficient catalyst support for cathodic oxygen reduction in low temperature PEMFC. Tests performed in MEAs showed that Pt supported on carbon nanofibers exhibited an enhancement of ca. 94% in power density at 0.600 V, in comparison with a commercial catalyst supported on conventional carbon black, Pt/Vulcan XC-72R.     

Kinetics and mechanism of oxygen electroreduction in alkaline solutions on xc-72r carbon black modified by products of pyrolysis of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin

Cathodic oxygen reduction on XC-72R carbon black modified by products of pyrolysis of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (CoTMPP) (XC-72M) was studied. When XC-72R carbon black is modified, new active centers (ACs) are formed on the surface of the carbon support, on which the direct reaction to OH^- occurs, as shown using the rotating ring-disk electrode technique. The process of oxygen reduction on nonmodified carbon black occurs via the serial path. At low polarizations, the dependence of potential on pH corresponds to the slope of ??30 mV both for the carbon material and modified carbon black. This value is close to the coefficient in the Nernst equation for H₂/HO ₂ ^? . The slow stage of oxygen reduction is the transfer of the first or second electron to the adsorbed molecule. Herewith, the difference in the kinetics and mechanism of oxygen reduction on XC-72R and XC-72M is related to a stronger adsorption interaction of oxygen and ACs on XC-72M. The {ie1113-1} value in the pH range of 12?C14.6 is ?15 to ?20 mV both for XC-72R and XC-72M. In the case of the second halfwave potential on XC-72R, it is ?50 to ?60 mV. The observed effects are explained by a change in the surface state of catalysts at an increase in adsorption of OH^? ions at an increase in pH.     

Nanostructure and surface composition of Pt and Ru binary catalysts on polyaniline-functionalized carbon nanotubes

Pt-Ru binary catalysts were prepared on a polyaniline-functionalized multiwalled carbon nanotube (PANi/MWCNT). PANi/MWCNT composites were synthesized by the polymerization of aniline in the presence of a carbon nanotube suspension using FeSO(4) and (NH(4))(2)S(2)O(8) as the oxidants. The Pt-Ru/PANi/MWCNT catalysts were formed by the chemical reduction of H(2)PtCl(6) and RuCl(3) using NaBH(4) as the reducing agent. The binary component catalyst is sharply distributed, with particle sizes ranging from 2.0 to 4.0 nm, and the Pt and Ru distributions are homogeneous when supported on PANi/MWCNT. In comparison, the binary catalyst supported on bare MWCNT displayed a Pt-rich core and a Ru-rich shell nanostructure. The surface composition deduced from CO stripping potentials confirms that the Ru surface content (χ(Ru)) is approximately 50% for the Pt-Ru alloy on PANi/MWCNT, and the catalyst on bare MWCNT shows nearly 70% Ru on the surface. Pt-Ru binary catalysts supported on PANi/MWCNT have higher activity, a higher Pt utilization efficiency, and much better durability when compared to other catalyst supports on bare MWCNT or on Vulcan XC-72.     

Preparation of CoSe nanoparticles by microwave-assisted polyol method: effect of Se/Co ratio, support type and synthesis conditions on oxygen reduction activity

Highly methanol-tolerant CoSe nanoparticles supported on different carbon substrates were synthesized by microwave heating of glycerol solutions of cobalt(II) acetate and sodium selenite at different Se/Co mole ratios in the presence of different concentrations of acetic acid and ammonia. The resulting CoSe catalysts were used for the electrochemical oxygen reduction reaction (ORR) in acidic solution in the presence of methanol. The ORR activity of the catalyst was increased by increasing its Se content up to 50?mol%. The presence of acetic acid or ammonia in the synthesis solution significantly affects the electrocatalytic performance of the CoSe catalyst; highest activity was observed when the catalyst was synthesized at NH₃/Co(II) mole ratio of 6. Among the catalysts prepared on different supports including carbon black (Vulcan XC-72R), and nanoporous carbons synthesized from resorcinol-formaldehyde and phloroglucinol-formaldehyde resins, the one supported on the carbon prepared from the last resin exhibited highest electrocatalytic activity for ORR.     

Metal Oxide Promoted Electrocatalysts for Methanol Oxidation

An important research target in DMFCs is to find better catalyst materials that are cheaper, less-prone to poisoning and more catalytically active. In this context, metal oxides with good catalytic properties and stronger interaction with Pt nanoparticles can generate active interfacial regions for electrocatalysis. Pt catalysts promoted by certain metal oxides show enhanced methanol electro-oxidation activity and CO tolerance behavior. In this paper we summarize the recent progress from our laboratory which explored the possibility of developing Pt–MoO₃/C and Pt–Nb₂O₅/C electrocatalysts in acidic media, and Pt–V₂O₅/C electrocatalyst in alkaline media for direct electro-oxidation of methanol. The oxide electrocatalysts have been prepared by a fast and efficient method of loading the metal oxide on carbon black (Vulcan XC-72) employing an intermittent microwave heating (IMH) method. These materials are found to achieve higher activity and stability towards methanol electro-oxidation.     

Preparation and characterization of composite polyaniline materials for catalytic purposes

Composite film electrodes were prepared by open-circuit Pt deposition on polymeric PANI films that were electrosynthesized from aniline acid solutions with suspended carbon particles (CPs). Gold, nickel, and a Ni-based alloy, Nichrome, were used as substrates, and carbon particles, carbon nanotubes (CNT), and Vulcan XC-72R carbon black, suspended in the monomer acid solution, were incorporated into the film. Pt particles were dispersed on films grown on Ni-based substrates by deposition from a Pt(IV) acid solution at open circuit (OC). CNT trapped into the PANI films have a favorable influence on Pt dispersion. The novel composite electrodes showed significant catalytic activity for methanol oxidation.     

High-loading Pt nanoparticles on mesoporous carbon with large mesopores for highly active methanol electro-oxidation

High metal-loading Pt/C electrocatalysts are important for the fabrication of thin-layered membrane electrode assemblies (MEAs). However, the preparation of high-loading Pt catalysts with a narrow size distribution of nanoparticles remains a challenge. Herein, ordered mesoporous carbon (OMC) with large mesopores (~15 nm) and a high surface area (1316.0 m² g^?1) was fabricated using a SiO₂ nanosphere array as a template. This material was developed to support a high loading of Pt nanoparticles (60 wt%) and was then used as an electrocatalyst for the methanol oxidation reaction (MOR). The prepared Pt/OMC contains Pt nanoparticles with an average size of ~1.9 nm that are uniformly dispersed on the mesoporous walls of the OMC. The Pt/OMC catalyst exhibits smaller Pt nanoparticle size, greater Pt dispersion, larger specific electrochemically active surface area (ECSA), and higher electrocatalytic activity for the MOR than the carbon black (Vulcan XC-72R)-supported Pt and the commercial Pt/C catalysts.     

活性炭载体对聚合物电解质膜燃料电池中炭载铂电催化剂性能的影响

分别以松木炭和Vulcan XC-72炭为载体制得载铂电催化作用，在聚合物电解质膜燃料电池（PEMFC）中对其性能进行了比较。结果表明：Vulcan XC-72炭作载体的电催化剂性能显著优于松木炭作载体的电催化剂，利用多种分析对活性炭的物理和表面化学性质进行了系统的研究，发现活性炭的孔径、电导率和表面含氧基团和电催化剂性能有很大的影响。     

Effects of type of nanosized carbon black on the performance of an all-solid-state potentiometric electrode for nitrate

The potentiometric properties of all-solid-state nitrate-selective electrodes based on plasticized PVC and containing different types of nanosized carbon black were investigated. The use of a carbon black interlayer is shown to significantly improve the potentiometric response. The electrodes display a close-to-Nernstian slope in the range from 10^?1 to 10^?6 M, highly stable potentials and low membrane resistance. However, different analytical features were found depending on the type of carbon black used. The best long-term potential stability was observed for the electrode with Printex XE2-B carbon black that has a relatively high BET surface area (1000 m²?·?g^?1) and an average particle size of 30 nm. Nevertheless, the electrodes with the Vulcan XC-72 (BET surface: 240 m²?·?g^?1; average size: 55 nm) showed the most repeatable and reproducible standard potential. The lowest detection limit for nitrate (2.5·10^?7 M) is observed for an electrode containing Vulcan XC-72.

Synthesis, electrochemical characterization and molecular dynamics studies of surface segregation of platinum nano-alloy electrocatalysts

Alloy Pt-M (M = Co, Ni) nanocatalysts, supported on carbon Vulcan XC-72, were synthesized using the carbonyl chemical route. A high dispersion on such substrate was revealed by transmission electron microscopy (TEM). Alloy formation on the nanometre scale length was shown by high-resolution transmission microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX) on a nanoparticle. The metal M in Pt-M nanoalloys segregates preferentially on the nanoparticles' surface, as determined by the hydrogen adsorption electrochemical reaction. An increased tolerance towards methanol of such nanoalloy materials was observed for the oxygen reduction reaction (ORR) in acid media. To better understand the structure and segregation phenomena of these nanoalloys, molecular dynamics (MD) with a self-optimized reactive force field was applied.     

WO3/C hybrid material as a highly active catalyst support for formic acid electrooxidation

The hybrid material based on WO₃ and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO₃/C catalysts in a large range of WO₃ content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on the WO₃/C support and the hydrogen spillover effect which greatly accelerates the dehydrogenation of HCOOH on Pd.