Platinum nanopaticles supported on stacked-cup carbon nanofibers as electrocatalysts for proton exchange membrane fuel cell

Inexpensive stacked-cup carbon nanofibers (SC-CNFs) supported Pt nanoparticles with a loading from 5 to 30 wt.% were prepared through a modified ethylene glycol method. XRD and TEM characterizations show that the average Pt particle sizes increase with increasing metal loading, and they can be controlled <5 nm with a uniform dispersion. A self-developed filtration process was employed to fabricate Pt/SC-CNFs film-based membrane electrode assembly (MEA), and the catalyst transfer efficiency can reach nearly 100% using a super-hydrophobic polycarbonate filter. The thickness of catalyst layer can be accurately controlled through altering Pt loadings of the catalyst and electrode, this is in good agreement with our theoretical calculation. For Pt/SC-CNFs-based-MEAs, Pt cathode loading was found more critical than Pt anode loading on proton exchange membrane fuel cell (PEMFC) performance. The Pt/SC-CNFs-based MEA with an optimized 50 wt.% Nafion content demonstrates higher PEMFC performance than the carbon black-based MEA with an optimized 30 wt.% Nafion content. SC-CNFs possess much larger length-to-diameter ratio than carbon black particles, it makes Pt/SC-CNFs more easily form continuously conductive networks in the Nafion matrix than carbon black. Therefore, the Pt/SC-CNFs-based MEA demonstrates higher Pt utilization than carbon black-based MEA, which implies possible reduction in Pt loading of MEA.     

XAS of carbon supported platinum fuel cell electrocatalysts: advances towards real time investigations

The utility of XAS to provide detailed information regarding thestructure of supported electrocatalysts has previously been demonstrated. Areview of the literature relating to carbon supported Pt fuel cellelectrocatalysts is presented. Improvements in the time resolution of the datacollection which have become possible with the introduction of energydispersive monochromators are discussed and a critical analysis of the effectof these improvements is presented. This revised version was published online in June 2006 with corrections to the Cover Date.     

Functionalized-carbon nanotube supported electrocatalysts and buckypaper-based biocathodes for glucose fuel cell applications

The preparation and testing for electrocatalytic activity of functionalized carbon nanotube (f-CNT) supported Pt and Au–Pt nanoparticles (NPs), and bilirubin oxidase (BOD), are reported. These materials were utilized as oxygen reduction reaction (ORR) cathode electrocatalysts in a phosphate buffer solution (0.2 M, pH 7.4) at 25 °C, in the absence and presence of glucose. Carbon monoxide (CO) stripping voltammetry was applied to determine the electrochemically active surface area (ESA). The ORR performance of the Pt/f-CNTs catalyst was high (specific activity of 80.9 μA cm_Pt⁻² at 0.8 V vs. RHE) with an open circuit potential within ca. 10 mV of that delivered by state-of-the-art carbon supported platinum catalyst and exhibited better glucose tolerance. The f-CNT support favors a higher electrocatalytic activity of BOD for the ORR than a commercially available carbon black (Vulcan XC-72R). These results demonstrate that f-CNTs are a promising electrocatalyst supporting substrate for biofuel cell applications.     

Adsorption of phenol and 1-naphthol onto XC-72 carbon

XC-72 carbon (XC-72) was characterized by SEM, XPS, N₂ adsorption-desorption, particle size distribution analysis and potentiometric acid-base titration. The adsorption of phenol and 1-naphthol on XC-72 was studied as a function of contact time, pH, adsorbent content and temperature. The kinetic adsorption data were described well by the pseudo-second-order model. The adsorption isotherms of phenol were described well by Freundlich model, while the adsorption isotherms of 1-naphthol were fitted well by Langmuir model. The results demonstrated that XC-72 had much higher adsorption capacity for 1-naphthol than for phenol. The adsorption thermodynamic data were calculated from the temperature-dependent adsorption isotherms at T=293, 313 and 333 K, and the results indicated that the adsorption of phenol was an exothermic process, whereas the adsorption of 1-naphthol was an endothermic process. XC-72 is a suitable material for the preconcentration of phenol and 1-naphthol from large volumes of aqueous solutions.     

Fluorination of Vulcan XC-72R for cathodic microporous layer of passive micro direct methanol fuel cell

The effect of adding fluorinated Vulcan XC-72R into the microporous layer (MPL) of the cathode in a passive micro direct methanol fuel cell (μDMFC) has been investigated. Upon fluorination with fluoro-alkyl silane (FAS), the surface of XC-72R becomes more hydrophobic, as indicated by contact angle measurements. The performance of the membrane electrode assembly (MEA) is improved significantly when fluorinated Vulcan XC-72R is used in MPL of the cathode. The maximum power density of a passive μDMFC reached ca. 36.2 mW cm⁻² at room temperature, and the constant-current discharging test exhibits enhanced stability. Also observed is a decreased water transport coefficient (α), calculated from discharging test, attributable to the greater hydrophobicity resulting in higher liquid pressure on the cathode, which forces more water to flow back to the anode. Additionally, A.C. impedance analysis indicates that the improvement in performance results from the decrease of charge transfer resistance of the cathodic reaction.     

Carbon nanofibers supported Pt-Ru electrocatalysts for direct methanol fuel cells

Oxidized and reduced carbon nanofibers (OCNF and RCNF) were used as supports to prepare highly dispersed PtRu catalysts for the direct methanol fuel cells (DMFC). The structural and surface features and electrocatalytic properties of bimetallic PtRu/OCNF and PtRu/RCNF were extensively investigated. FT-IR spectra show that carboxyl groups exist on the surface of the OCNF, which greatly influence the morphology and crystallinity of the electrocatalysts. Transmission electron microscopy and X-ray diffraction consistently show that PtRu/RCNF has a smaller particle size and more uniform distribution than PtRu/OCNF. However, both catalysts have very similar methanol oxidation peak current densities that are significantly lower than commercial catalyst based on current-voltage (CV) results. These two catalysts also give very similar single cell performance except for some difference in the resistance polarization region. The OCNF supported catalysts give better performance than commercial catalysts when current density is higher than 50 mA cm⁻² in spite of low methanol oxidation peak current density. These results can be ascribed to the specific surface and structural properties of carbon nanofibers.     

Progress in the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for PEM fuel cell catalysis

This paper reviews the literature on the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for proton exchange membrane (PEM) fuel cell catalyst loading reduction through the improvement of catalyst utilization and activity, especially focusing on cathode nano-electrocatalyst preparation methods. The features of each synthetic method were also discussed based on the morphology of the synthesized catalysts. It is clear that synthesis methods play an important role in catalyst morphology, Pt utilization and catalytic activity. Though some remarkable progress has been made in nanotube- and nanofiber-supported Pt catalyst preparation techniques, the real breakthroughs have not yet been made in terms of cost-effectiveness, catalytic activity, durability and chemical/electrochemical stability. In order to make such electrocatalysts commercially feasible, cost-effective and innovative, catalyst synthesis methods are needed for Pt loading reduction and performance optimization.     

Characterization of Pt-Cu-Fe ternary electrocatalysts supported on carbon black

Ternary Pt-Cu-Fe alloy catalysts, useful for low temperature fuel cells, were prepared from aqueous media, followed by heat treatment at 900 °C for various heating periods. Supported metal crystallites were characterized with various techniques including XRD, XPS, TEM and ICP-AES. XRD patterns indicate that the lattice structure of platinum changes from a face-centred cubic to a contracted facecentred tetragonal structure as it forms an alloy. As the heating period increases, the extent of formation of an ordered alloy increases and the formation is completed in 2.5 h, as confirmed by the intensity of superlattice diffraction lines. The presence of different oxidation states is confirmed by XPS and the amount of higher oxidation state is reduced by heat-treatment, but there is no evidence of development of a new photoelectron peak or shift in binding energy by alloy formation. For the electrochemical reduction reaction of oxygen in fuel cell operation, ordered alloys have shown improved catalytic activity compared to platinum alone. After the stability test in hot phosphoric acid, the ordered structure is preserved even though a significant amount of transition metal is dissolved, and some increase in particle size in the heat-treated catalysts is observed.     

Polyaniline–13X zeolite composite‐supported platinum electrocatalysts for direct methanol fuel cell applications

We successfully synthesized 13X zeolite using a hydrothermal method. Then, composites of polyaniline (PANI) with 13X zeolite and PANI–13X with platinum were prepared by chemical oxidative polymerization and chemical reduction, respectively. Field emission scanning electron microscopy, X‐ray diffraction, Raman spectroscopy and Brunauer–Emmett–Teller techniques were used to characterize the PANI–Pt and PANI–Pt–13X composites. Further, the electrocatalytic activity towards methanol oxidation of the synthesized catalysts was explored using cyclic voltammetry in 1 mol L^?1 CH₃OH + 0.5 mol L^?1 H₂SO₄ solution. From the obtained results, PANI–Pt–13X shows superior performance compared to PANI–Pt towards methanol oxidation and electrical conductivity. Hence, the 13X zeolite‐incorporated PANI–Pt composite could be an efficient catalyst for direct methanol fuel cell applications. © 2019 Society of Chemical Industry     

用于PEMFC的介孔碳担载铂氧化钨电催化剂的制备与表征

利用介孔碳作为载体,制备介孔碳担载Pt-WO3复合催化剂应用于质子交换膜燃料电池（PEMFC）电极.以苯为碳源,采用气相沉积法复制介孔SiO2Al-SBA-15模板结构合成石墨化介孔碳Cg,采用浸渍法制备无定形介孔碳CMK-3.通过分步沉积,将Pt和WO3担载到介孔碳载体上,采用比表面分析（BET）、X线衍射（XRD）、透射电子显微镜（TEM）、循环伏安法以及单电池极化性能测试对介孔碳担载的复合催化剂进行表征.结果表明：介孔碳作为催化剂载体,其孔道结构有助于催化剂的均匀分散,从而提高催化剂的电催化剂活性.由于石墨化介孔碳的导电性能高于无定形介孔碳,因此Pt-WO3/Cg比Pt-WO3/CMK-3具有更好的电极催化活性.     

直接硼氢化物燃料电池阳极电催化剂研究进展

以硼氢化物作为燃料电池的燃料因其高的理论电动势和比能量而引起研究者的广泛关注。理论上,BH-4的电氧化反应为八电子反应,但实际上由于所用阳极电催化剂的不同,BH-4电氧化释放出的电子数也不同。如何抑制BH-4在阳极的水解反应,促进其八电子氧化反应一直是直接硼氢化物燃料电池研究中的核心问题。综述了近几年来国内外在直接硼氢化物燃料电池阳极电催化剂方面所取得的研究进展,并对这一领域中需要深入研究的主要问题进行了论述。     

低温燃料电池催化剂的研究进展

综述了近年来低温燃料电池,如质子交换膜燃料电池（PEMFC）和直接甲醇燃料电池（DMFC）催化剂的研究进展,着重介绍了近年来出现的几种制备高分散和高活性的燃料电池催化剂的新技术和新方法,以及关于低Pt和非Pt催化剂的研究情况,简要介绍了关于燃料电池催化剂基础研究方面的情况。     

A novel supported palladium catalyst for alternating copolymerization of styrene and carbon monoxide

A new heterogeneous catalyst, polyaniline supported palladium (II) chloride (PANI–PdCl₂), was synthesized and studied for alternating copolymerization of styrene (ST) with carbon monoxide (CO) to prepare polyketone (PK). The SEM, FTIR and XRD results indicated that PdCl₂ was successfully supported on PANI backbone. The ¹H NMR, FTIR, ¹³C NMR, TG and DTG results indicated that the supported catalyst changed the microstructures of PK, and the product is a linear alternating copolymer with higher degradation rates and decomposition temperatures. Furthermore, PANI–PdCl₂ catalyst was found to serve as an effective recycled catalyst after the third recover time.     

Platinum and platinum-ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum-ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt-Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation.     

Comparison of different methods for determination of Pt surface site concentrations for supported Pt electrocatalysts

Platinum surface atom (or site) concentrations for a series of commercially available 10, 20, and 40 wt% Pt/C electrocatalysts have been determined using X-ray diffraction (XRD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), selective chemisorption, and cyclic voltammetry (CV) methods. Each method of analysis was repeated for a sufficient number of times to determine reproducibility and standard deviation limits. Comparison of the results shows that XRD and STEM methods give Pt surface site concentrations much higher than for chemisorption analysis due to assumptions regarding Pt particle shapes and particle size distributions. The results from CV analysis agree reasonably well with those from chemisorption if the sample amounts and methods of sample deposition preceding CV analysis can be well-controlled and there is no loss of surface exposure by the Nafion over-layer. Because both chemisorption and CV analyses more directly measure actual site concentrations with fewer assumptions, these methods should be considered superior to XRD and STEM analyses. Further, since chemisorption uses substantially larger sample sizes (up to 0.25 g) compared to CV (<0.01 g), reliability of chemisorption data is much more reliable and should be considered as the metric for surface Pt site determination.     

Preparation of Pt/C cathode catalyst supported on chestnut-like mesoporous carbon for fuel cell applications

Fuel cells have received worldwide attention as a next-generation renewable energy technology. However, catalyst cost and durability are the main issue hampering the commercialization of fuel cells. Many studies have focused on the physicochemical properties of the carbon support to improve the catalyst’s properties. Mesoporous carbons are suitable candidates because of their appropriate structural characteristics, including high surface area, large pore size, and regularly interconnected mesopores that permit efficient diffusion of the reactants and by-products. In this study, supports made from chestnut-like carbon consisting of platelet carbon nanofibers were fabricated by selective catalytic gasification of activated carbon. Pt/C catalysts were synthesized from these support structures using the impregnation method. Catalyst performance and characteristics were investigated by N₂ adsorption/desorption isotherms, X-ray diffractions, and the rotating disk electrode technique for the oxygen reduction reaction.     

Pt–Ru nanoparticles supported on functionalized carbon as electrocatalysts for the methanol oxidation

Platinum–ruthenium alloy electrocatalysts, for methanol oxidation reaction, were prepared on carbons thermally treated in helium atmosphere or chemically functionalized in H₂O₂, or in HNO₃ + H₂SO₄ or in HNO₃ solutions. The functionalized carbon that is produced using acid solutions contains more surface oxygenated functional groups than carbon treated with H₂O₂ solution or HeTT. The XRD/HR-TEM analysis have showed the existence of a higher alloying degree for Pt–Ru electrocatalysts supported on functionalized carbon, which present superior electrocatalytic performance, assessed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, as compared to electrocatalysts on unfunctionalized carbon. It also was found that Pt–Ru alloy electrocatalysts on functionalized carbon improve the reaction rate compared to Pt–Ru on carbons treated with H₂O₂ solution and thermally. A mechanism is discussed, where oxygenated groups generated from acid functionalization of carbon and adsorbed on Pt–Ru electrocatalysts are considered to enhance the electrocatalytic activity of the methanol oxidation reaction.     

Tetrahydrofuran-functionalized multi-walled carbon nanotubes as effective support for Pt and PtSn electrocatalysts of fuel cells

A novel and simple method to functionalize multi-walled carbon nanotubes (MWCNTs) is developed using tetrahydrofuran (THF) solvent as the functionalization and anchoring agent. The effectiveness of the method is demonstrated by the synthesis of uniformly distributed Pt and PtSn nanoparticles on THF-functionalized MWCNTs. Transmission electron microscopy and X-ray diffraction results indicate that Pt and PtSn nanoparticles with a narrow particle size distribution and an average particle size of ∼4 nm are synthesized on THF-functionalized MWCNTs. The lattice parameter of PtSn/MWCNTs increases with the Sn content, indicating the successful formation of PtSn binary nanoparticles. The results demonstrate the applicability and effectiveness of the THF-functionalized MWCNTs as effective catalyst supports in the development of highly dispersed and active Pt and Pt-based electrocatalysts for low temperature fuel cells. The successful functionalization of MWCNTs by THF also indicates that there could be a strong σ-π interaction between the MWCNTs and the THF.     

Carbon supported Pt–Co alloys as methanol-resistant oxygen-reduction electrocatalysts for direct methanol fuel cells

The electrocatalysis of the oxygen reduction reaction on carbon supported Pt and Pt–Co (Pt/C and Pt–Co/C) alloy electrocatalysts was investigated in sulphuric acid (both in the absence and in the presence of methanol) and in direct methanol fuel cells (DMFCs). In pure sulphuric acid Pt–Co/C alloys showed improved specific activity towards the oxygen reduction compared to pure platinum. In the methanol containing electrolyte a higher methanol tolerance of the binary electrocatalysts than Pt/C was observed. The onset potential for methanol oxidation at Pt–Co/C was shifted to more positive potentials. Accordingly, Pt–Co/C electrocatalyts showed an improved performance as cathode materials in DMFCs.