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41.
Benedetto Bozzini Matteo AmatiMarco Boniardi Majid Kazemian AbyanehLuca Gregoratti Maya Kiskinova 《Journal of power sources》2011,196(5):2513-2518
In this paper we report an investigation of the degradation of the Pt/C electrocatalyst of an anodic membrane-electrode assembly (MEA) after 1000 h of operation in a laboratory single-cell PEMFC, using synchrotron-based space-resolved photoelectron spectroscopy. This study is complemented by the analysis of a pristine MEA and reference materials, as well as by electrochemical measurements, SEM imaging and energy-dispersive X-ray fluorescence spectroscopy (EDX). Catalyst ageing correlates with a corrugation of morphology, as observed by SEM and scanning photoelectron microscopy (SPEM), corresponding to Pt nanoparticle agglomeration. Moreover - on the basis of high lateral resolution SPEM, X-ray photoelectron spectroscopy (XPS) and EDX analyses, - we found that, after operation, Pt is transported onto the fibres of the gas-diffusion layer (GDL). Space-resolved XPS shows a peak shift of the Pt 4f7/2 level to higher and lower binding energies with respect to Pt(1 1 1) and pristine Pt black, respectively, corresponding to nanocrystallinity in the first case and agglomeration in the second one. No oxidised Pt was found in any location of the anodically used MEA. 相似文献
42.
Gokce S. Avcioglu Berker Ficicilar Inci Eroglu 《International Journal of Hydrogen Energy》2018,43(23):10779-10797
Cathode catalyst layer has an important role on water management across the membrane electrode assembly (MEA). Effect of Pt percentage in commercial catalyst and Pt loading from the viewpoint of activity and water management on performance was investigated. Physical and electrochemical characteristics of conventional and hydrophobic catalyst layers were compared. Performance results revealed that power density of conventional catalyst layers (CLs) increased from 0.28 to 0.64 W/cm2 at 0.45 V with the increase in Pt amount in commercial catalyst from 20% to 70% Pt/C for H2/Air feed. In the case of H2/O2 feed, power density of CLs increased from 0.64 to 1.29 W/cm2 at 0.45 V for conventional catalyst layers prepared with Tanaka. Increasing Pt load from 0.4 to 1.2 mg/cm2, improved kinetic activity at low current density region in both feeding conditions. Scattering electron microscopy (SEM) images revealed that thickness of the catalyst layers (CLs) increases by increasing Pt load. Electrochemical impedance spectroscopy (EIS) results revealed that thinner CLs have lower charge transfer resistance than thicker CLs. Inclusion of 30 wt % Polytetrafluoroethylene (PTFE) nanoparticles in catalyst ink enhanced cell performance for the electrodes manufactured with 20% Pt/C at higher current densities. However, in the case of 70% Pt/C, performance enhancement was not observed. Cyclic voltammetry (CV) results revealed that 20% Pt/C had higher (77 m2/g) electrochemical surface area (ESA) than 70% Pt/C (65 m2/g). In terms of hydrophobic powders, ESA of 30PTFE prepared with 70% Pt/C was higher than 30PTFE prepared with 20 %Pt/C. X-Ray Diffractometer (XRD) results showed that diameter of Pt particles of 20% Pt/C was 2.5 nm, whereas, it was 3.5 nm for 70% Pt/C, which confirms CV results. Nitrogen physisorption results revealed that primary pores of hydrophobic catalyst powder prepared with 70% Pt/C was almost filled (99%) with Nafion and PTFE. 相似文献
43.
Dao-Jun Guo Xin-Ping Qiu Wen-Tao Zhu Li-Quan Chen 《Applied catalysis. B, Environmental》2009,89(3-4):597-601
Sulfated zirconia supported on multi-walled carbon nanotubes as new supports of Pt catalyst (Pt–S-ZrO2/MWCNT) was synthesized with aims to enhance electron and proton conductivity and also catalytic activity of Pt electrocatalyst in terms of larger concentrations of ionizable OH groups on surfaces. Fourier transform infrared spectroscopy analysis shows that the sample surfaces were modified with sulfate. Transmission electron microscopy results show that the Pt and sulfated ZrO2 particles dispersed relatively uniformly on the surface of the multi-walled carbon nanotube. X-ray diffraction shows that S-ZrO2 and Pt coexist in the Pt–S-ZrO2/MWCNT composites and S-ZrO2 has no effect on the crystalline lattice of Pt. Pt–S-ZrO2/MWCNT catalyst was evaluated in terms of the electrochemical activity for methanol electro-oxidation using cyclic voltammetry, steady-state polarization experiments and electrochemical impedance spectroscopy technique at room temperature. Pt–S-ZrO2/MWCNT catalyst show higher catalytic activity for methanol electro-oxidation compared with Pt catalyst on non-sulfated ZrO2/MWCNT support and commercial Pt/C (E-TEK). 相似文献
44.
S. García-Rodríguez S. Rojas M. Vellosillo M.A. Peña J.L.G. Fierro P. Ocón 《International Journal of Hydrogen Energy》2010
This work aims to shed light on the wide dispersion of the values of the area of Pt/C electrodes reported when evaluated by means of the thin-film electrode approach. The effect of the Perfluorosulfonic Ionomer (PFSI) content of the electrodes and the nature of the electrolyte are discussed. The results disclose that the area of the Pt electrodes evaluated by electrochemical techniques is related to the actual PFSI content on the electrode and to the nature of the electrolyte. Using HClO4 as electrolyte, electrode area values are independent of the PFSI content. On the contrary, if experiments are recorded in H2SO4, the electrode area value increases with the increasing PFSI content, irrespectively of the Pt loading. Such effect is ascribed to the interaction of the sulfonic groups from the PFSI with the surface of the Pt nanoparticles, avoiding the strong adsorption of the bisulfate anions. 相似文献
45.
As a continuation of a project on the spectroelectrochemical analysis of long-term behaviour of WC-supported Pt electrocatalysts (for SFG results, see part I: [1]), in this paper we report in situ FT-IR spectroscopy experiments, carried out during prolonged electro-oxidation of ethanol on Pt-black. From the analytical point of view, as expected, FT-IR spectra showed the presence of adsorbed acetic acid and ethanol, in addition to the well-known, dominant species: linearly adsorbed CO (2044-2063 cm−1) and solution-phase CO2 (2345 cm−1). As far as quantitative spectroscopic results are concerned, a notable sensitivity of the interfacial chemistry to catalyst aging could be highlighted by this approach. The spectra recorded in three subsequent series of potential-cycling experiments showed a clear-cut dependence of spectral patterns and peak intensities, on the applied potential and on the oxidation duration. Qualitative spectral changes seem to suggest - coherently with in situ SFG results obtained with the same system [1] - that electrocatalyst aging correlates with a higher surface coverage with ethanol as compared with acetic acid. Quantitative analysis, based on fitting with Lorentzian lineshapes, yields information that can be used as a molecular-level diagnostic of the modification of the catalyst-adsorbate structure. 相似文献
46.
Yuan-Hang Qin Hou-Hua Yang Xin-Sheng Zhang Ping Li Chun-An Ma 《International Journal of Hydrogen Energy》2010
Pd electrocatalysts supported on three types of carbon nanofibers (CNFs), viz. platelet CNFs (p-CNFs), fish-bone CNFs (f-CNFs) and tubular CNFs (t-CNFs) are prepared and the effect of CNFs microstructure on the activities of the electrocatalysts for ethanol oxidation reaction (EOR) is investigated. The information on structural characteristics is obtained by high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. Electrochemical techniques are employed to characterize the microstructure effect of CNFs on the catalytic activities of catalysts. HRTEM images indicate the microstructure of CNFs has a powerful influence on the distribution of Pd particles. The results of the electrochemical characterization also indicate that the structure of CNFs significantly influences the catalytic activities of the electrocatalysts and p-CNFs supported Pd electrocatalyst has the best performance for ethanol oxidation in an alkaline medium because p-CNFs has the highest ratio of edge atoms to basal atoms and correspondingly the fastest electrode kinetics and strongest Pd–CNFs interaction. 相似文献
47.
A Combined Surface Science and Electrochemical Study of Tungsten Carbides as Anode Electrocatalysts 总被引:1,自引:0,他引:1
Erich C. Weigert Michael B. Zellner Alan L. Stottlemyer Jingguang G. Chen 《Topics in Catalysis》2007,46(3-4):349-357
An effective anode electrocatalyst in direct methanol fuel cell (DMFC) should have high activity for the oxidation of methanol
and the decomposition of water, while remaining stable under the relatively harsh anode environment. Although the Pt/Ru bimetallic
alloy is currently the most effective anode electrocatalyst, both Pt and Ru are expensive due to limited supplies and both
are susceptible to CO poisoning. Consequently, the discovery of less expensive and more CO tolerant alternatives to the Pt/Ru
catalysts would help facilitate the commercialization of DMFC. In this paper we will discuss the possibility of using tungsten
carbides (WC) and Pt-modified WC as potential anode electrocatalysts in DMFC. We will provide an overview of our recent work,
using a combined approach of fundamental surface science studies and in-situ electrochemical evaluation of the activity and
stability of tungsten carbides. We will demonstrate the feasibility to bridge fundamental surface science studies on single
crystals with the electrochemical evaluation on polycrystalline WC films. We will also discuss the synergistic effect by supporting
low coverages of Pt on the WC substrate to further enhance the electrochemical performance of WC. 相似文献
48.
Mixed IrO2-SiO2 oxide films were prepared on titanium substrate by the thermo-decomposition of hexachloroiridate (H2IrCl6) and tetraethoxysilane (TEOS) mixed precursors in organic solvents. The solution chemistry and thermal decomposition kinetics of the mixed precursors were investigated by ultra violet/visible (UV/vis) spectroscopy and thermogravimetry (TGA) and differential thermal analysis (DTA), respectively. The physiochemical characterization of the resulting materials was conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. It is shown from the UV/vis spectra that the electronic absorption intensity of IrCl62− complexes in the precursors decreases in the presence of TEOS, indicating the interaction between these two components. Thermal analysis shows the decomposition reaction of H2IrCl6 is inhibited by TEOS in the low temperature range, but the further oxidation reaction at high temperatures of formed intermediates is independent of the presence of silane component. Physical measurements show a restriction effect of silica on the crystallization and crystal growth processes of IrO2, leading to the formation of finer oxide particles and the porous morphology of the binary oxide films. The porous composite films exhibit high apparent electrocatalytic activity toward the oxygen evolution reaction. In addition, the long-term stability of Ti-supported IrO2 electrodes is found to apparently improve with appropriate amount of SiO2 incorporation, as tested under galvanostatic electrolysis. 相似文献
49.
A combinatorial library containing 645 different compositions was synthesised and characterised for methanol tolerant oxygen electro‐reduction reaction (ORR) catalytic performance. The library was composed of compositions involving between 1 and 4 metals among Pt, Ru, Fe, Mo and Se. In an optical screening test, Pt(50)Ru(10)Fe(20)Se(10) composition exhibited the highest ORR activity in the presence of methanol. This composition was further investigated by synthesis and characterisation of a powder version catalyst [Pt(50)Ru(10)Fe(20)Se(10)/C]. At 0.85 V [vs. reversible hydrogen electrode (RHE)] in the absence of methanol, the Pt/C catalyst exhibited higher ORR current (0.0990 mA) than the Pt(50)Ru(10)Fe(20)Se(10)/C catalyst (0.0902 mA). But much higher specific activity (12.7 μA cmpt–2) was observed in the Pt(50)Ru(10)Fe(20)Se(10)/C catalyst than for the Pt/C catalyst 6.51 μA cmpt–2). In the presence of methanol, the ORR current decreased by 0.0343 and 0.247 mA for the Pt(50)Ru(10)Fe(20)Se(10)/C and Pt/C catalysts, respectively, which proved the excellent methanol tolerance of the Pt(50)Ru(10)Fe(20)Se(10)/C catalyst. 相似文献
50.
A palygorskite/carbon heterogeneous nanocomposite, a unique hybrid of palygorskite and carbon, was prepared and designed as an electrocatalyst support material for PtRuIr nanoparticles and evaluated for methanol electrooxidation. X‐ray diffraction and transmission electron microscopy results showed that PtRuIr nanoparticles were well‐dispersed on the composite support with highly dispersed tiny crystal alloy phase on the surface of PtRuIr amorphous alloy. X‐ray photoelectron spectroscopy results indicated that the formation of Ru and Ir oxides on the surface of the PtRuIr nanoparticles. The electrochemical results show that the palygorskite hybridized carbon used as electrocatalysts support can improve the electrocatalytic activity towards methanol oxidation and CO tolerance. 相似文献