SYNTHESIS AND CHARACTERIZATION OF CARBON SUPPORTED Pd AND PtPd CATALYSTS FOR DMFCs (original) (raw)
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Journal of Applied Electrochemistry, 2009
This work tries to study the problem of methanol crossover through the polymer electrolyte in direct methanol fuel cells (DMFCs) by developing new cathode electrocatalysts. For this purpose, a series of gas diffusion electrodes (GDEs) were prepared by using single-walled carbon nanotubes (SWCNTs) supported Pt-Pd (Pt-Pd/ SWCNT) with different Pd contents at the fixed metal loading of 50 wt%, as bimetallic electrocatalysts, in the catalyst layer. Pt-Pd/SWCNT was prepared by depositing the Pt and Pd nanoparticles on a SWCNTs support. The elemental compositions of bimetallic catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES) system. The performances of the GDEs in the methanol oxidation reaction (MOR) and in the oxygen reduction reaction with/without the effect of methanol oxidation reaction were investigated by means of electrochemical techniques: cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The results indicated that GDEs with Pt-Pd/SWCNT possess excellent electrocatalytic properties for oxygen reduction reaction in the presence of methanol, which can originate from the presence of Pd atoms and from the composition effect.
International Journal of Hydrogen Energy, 2011
Direct methanol fuel cell a b s t r a c t In the present work, a detailed characterization of the electrochemical behavior of carbon supported PdePt electrocatalysts toward CO and methanol electrooxidation in direct methanol fuel cells is reported. Technical electrodes containing an ionomer in their catalyst layer were prepared for this purpose. CO and methanol electrooxidation reactions were used as test reactions to compare the electrocatalytic behavior of bimetallic supported nanoparticles in acidic liquid electrolyte and in solid polymer electrolyte (real fuel cell operating conditions). Experimental results in both environments are consistent and show that the electrochemical behavior of carbon supported PdePt depends on their composition, giving the best performance in direct methanol single fuel cell with a Pd:Pt atomic ratio of 25:75 in the catalyst.
Journal of Electroanalytical Chemistry, 2017
Carbon-supported 30% Pd-based catalysts such as Pd/C, Pd 4 Co 1 /C and Pd 10 Co 1 /C were prepared by the sulphite complex route and physico-chemically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The electrochemical investigation was carried out in half cell and direct methanol fuel cell (DMFC) to evaluate the performance, the tolerance to permeated methanol and the durability of the Pd-based electrocatalysts. For comparison, a commercial 30% Pt/C catalyst was also electrochemically investigated. The advantage of using a high methanol concentration in DMFCs is related to a high energy density. Unfortunately, methanol crossover causes a mixed potential at Pt cathode catalysts reducing the overall cell efficiency, which is exacerbated with high methanol concentration (10 M) at the anode side. Pd and Pd-Co alloys based electrocatalysts exhibited high methanol tolerance properties, as evidenced in the half cell characterization, which led also to high performances in single cell configuration (DMFC). Thus, Pd-based electrodes represent a reliable way to minimize the cost in low temperature fuel cells, providing a higher performance than that of Pt-based electrodes at high methanol concentration.
Carbon-supported Pd–Co as cathode catalyst for APEMFCs and validation by DFT
Physical Chemistry Chemical Physics, 2012
Carbon supported PdCo catalysts in varying atomic ratios of Pd to Co, namely 1 : 1, 2 : 1 and 3 : 1, were prepared. The oxygen reduction reaction (ORR) was studied on commercial carbonsupported Pd and carbon-supported PdCo nanocatalysts in aqueous 0.1 M KOH solution with and without methanol. The structure, dispersion, electrochemical characterization and surface area of PdCo/C were determined by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Cyclic Voltammetry (CV), respectively. The electrochemical activity for ORR was evaluated from Linear Sweep Voltammograms (LSV) obtained using a rotating ring disk electrode. The catalysts were evaluated for their electrocatalytic activity towards oxygen reduction reaction (ORR) in Alkaline Polymer Electrolyte Membrane Fuel Cells (APEMFCs). PdCo(3 : 1)/C gives higher performance (85 mW cm À2) than PdCo(1 : 1)/C, PdCo(2 : 1)/C and Pd/C. The maximum electrocatalytic activity for ORR in the presence of methanol was observed for PdCo(3 : 1)/C. First principles calculations within the framework of density functional theory were performed to understand the origin of its catalytic activity based on the energy of adsorption of an O 2 molecule on the cluster, structural variation and charge transfer mechanism.
Pt decorated PdFe/C: Extremely High Electrocatalytic Activity for Methanol Oxidation
International journal of electrochemical science
A carbon supported Pt-decorated PdFe alloy nano-core catalysts (Pt-PdFe/C) for methanol oxidation is prepared via metathetical reaction between PdFe alloy nanoparticles (deposited on carbon) and PtCl 4 2in aqueous solution. Morphology and composition of the synthesized catalyst are characterized by Transmission Electron Microscope and X-ray diffraction. Experimental results show the electrochemical active surface area of the Pt-PdFe/C catalyst is much larger than those of the PdFe/C and Pt/C catalysts. Furthermore, the mass specific peak current is 1.01 A mg -1 for methanol oxidation on the Pt-PdFe/C electrode, an increase by a factor of 3.5 times and 12.6 times as compared to PtRu/C and Pt/C, respectively. The facile fabrication and high electrochemical performance of Pt-PdFe/C highlight its potential application as anode for DMFCs.
Fuel Cells, 2013
This work reports the synthesis of Pd-based alloy electrocatalysts of Co supported on multi-walled carbon nanotubes (MWCNTs) and their evaluation as cathode materials in a passive direct methanol fuel cell (PDMFC). The X-ray diffraction (XRD) analysis showed well-defined reflections corresponding to a face centered cubic phase of palladium. As compared to the Pd/MWCNT electrocatalyst, the bimetallic alloy electrocatalysts with the different Pd x Co atomic ratios showed highly enhanced mass activity (MA) for the oxygen reduction reaction (ORR); however, the significant enhancement in the specific activity (SA) by a factor of about 1.2-5.6 for the ORR was found on the Pd x Co alloy electrocatalysts in the presence and absence of methanol electrolyte solution. This enhancement SA in of the Pd-based electrocatalysts was correlated to the changes in the lattice parameter and Pd x Co surface composition. Surface area changes of Pdbased electrocatalysts supported on MWCNT were evaluated using an accelerated durability test (ADT). The results obtained using the ADT were correlated to the performance of the Pd-based electrocatalysts in the PDMFC. A better performance was obtained for the cell using Pd 3 Co/MWCNT (2.53 mW cm-2) compared to Pd/MWCNT (1.64 mW cm-2) and Pt/C-Electrochem (1.20 mW cm-2) as cathode in the PDMFC. In the presence and absence of methanol the impedance Bode spectra showed one time constant that associated to follow a four electron pathway.
Journal of The Electrochemical Society, 2007
The carbon-supported nanoparticles of Pd-Co-M ͑M = Pt, Au, Ag͒ catalysts for direct methanol fuel cells ͑DMFCs͒ in a ratio of ͑70:20:10͒ were prepared through reverse microemulsion method. The X-ray diffraction ͑XRD͒ analysis showed well-defined reflections corresponding to a face centered cubic phase of palladium. From transmission electron microscopy analysis, the particle size after heat-treatment at 500°C was found to be approximately 20 nm, which was also confirmed by XRD analysis. Polarization data indicated Pd-Co-Pt to have better oxygen reduction reaction ͑ORR͒ activity than the other combinations with Ag and Au, in terms of shift in onset potential to a positive value of more than 100 mV and increased reduction current. The ORR kinetics on Pd-Co-Pt was analyzed by using rotating disk electrode to follow a 4 electron pathway, the order of the reaction being unity. The peroxide formation estimated from the rotating ring disk electrode measurements was found to be a negligibly small amount of 1.1%. An additional advantage observed with Pd-Co-Pt was its high methanol tolerance and ORR activity nearly equal to Pt.
Synthesis of PtRu/C-CNTs electrocatalysts for DMFCs with treated-CNTs and composition regulation
Advances in Natural Sciences: Nanoscience and Nanotechnology, 2014
In the present work, PtRu/C-CNTs catalyst samples were studied for potential applications in direct methanol fuel cells (DMFCs). Carbon nanotubes (CNTs) were treated by H 2 SO 4 98% and HNO 3 65% at different temperatures and with different stirring periods. As a result, the PtRu/C-CNTs catalyst was successfully synthesized by using H 2 PtCl 6 and RuCl 3 precursors with the efficient reduction of NaBH 4 agent in ethylene glycol (e.g.). In addition, we controlled the ratios of treated-CNTs on carbon vulcan XC-72 treated-CNTs substrate (C-CNTs) with the different values: 50 wt%, 25 wt%, and 12.5 wt%, respectively. The PtRu/C-CNTs electrocatalyst samples were investigated by experimental methods including x-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry (CV). Importantly, the CV results show the best treated-CNTs and the most suitable ratio of CNTs composition on C-CNTs substrate to be controlled in order to produce various efficient PtRu/C-CNTs catalysts with high catalytic activity for DMFCs.