SYNTHESIS AND CHARACTERIZATION OF CARBON SUPPORTED Pd AND PtPd CATALYSTS FOR DMFCs (original) (raw)
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.
International Journal of Hydrogen Energy, 2017
In this study, nitrogen doped graphene (NG) and multi-walled carbon nanotubes (MWCNT) were used as supporting materials for palladium active phase to investigate their performance in direct methanol fuel cells (DMFCs). The facile and low temperature solvothermal method was used for the synthesis of NG. Palladium nanoparticles were deposited on the surface of NG and MWCNT by a modified polyol reduction method. The morphologies and microstructures of the prepared catalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Also, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were carried out to evaluate the electrocatalytic activity and the durability of the obtained catalysts towards methanol oxidation reaction. Pd/NG catalyst had a better activity and durability of methanol electrocatalytic oxidation rather than Pd/ MWCNT catalyst, which is related to good dispersion of Pd nanoparticles on the surface of nitrogen doped graphene and the physicochemical characteristics of NG.
International Journal of Hydrogen Energy, 2017
Platinum e cobalt (PtCo) alloy based highly efficient nano electro-catalysts on reduced graphene oxide (rGO) matrix have been synthesized for the electro-oxidation of methanol, by chemical reduction method. Different molar ratio of Pt (IV) and Co (II) ions along with graphene oxide (GO) were reduced using ethylene glycol to obtain PtCo nanoparticles onto rGO sheets (Pt/rGO, PtCo (1:1)/rGO, PtCo (1:5)/rGO, PtCo (1:9)/rGO and PtCo (1:11)/rGO) with 20 wt. % metal and 80 wt. % rGO. The average particle size of PtCo nanoparticles onto rGO support was observed to be 2e5 nm using XRD and TEM analysis. The PtCo (1:9)/rGO nanocomposite catalyst exhibited~23 times higher anodic current density compare to commercially available Pt/C catalyst (1.68 mA/cm 2) for methanol oxidation reaction. The peak power density of 118.4 mW/cm 2 was obtained for PtCo (1:9)/rGO catalyst in direct methanol fuel cell (DMFC) at 100 C, 1 bar, and 2 M methanol as anode feed, which is~3 times higher than that of Pt/C catalyst. The results indicate the potential application of synthesized nanocomposite catalyst in commercial DMFCs.
Carbon-Supported Pd and PdFe Alloy Catalysts for Direct Methanol Fuel Cell Cathodes
Materials (Basel, Switzerland), 2017
Direct methanol fuel cells (DMFCs) are electrochemical devices that efficiently produce electricity and are characterized by a large flexibility for portable applications and high energy density. Methanol crossover is one of the main obstacles for DMFC commercialization, forcing the search for highly electro-active and methanol tolerant cathodes. In the present work, carbon-supported Pd and PdFe catalysts were synthesized using a sodium borohydride reduction method and physico-chemically characterized using transmission electron microscopy (TEM) and X-ray techniques such as photoelectron spectroscopy (XPS), diffraction (XRD) and energy dispersive spectroscopy (EDX). The catalysts were investigated as DMFC cathodes operating at different methanol concentrations (up to 10 M) and temperatures (60 °C and 90 °C). The cell based on PdFe/C cathode presented the best performance, achieving a maximum power density of 37.5 mW·cm(-2) at 90 °C with 10 M methanol, higher than supported Pd and Pt...
Enhanced methanol electro-oxidation activity of PtRu catalysts supported on heteroatom-doped carbon
Electrochimica Acta, 2008
PtRu nanoparticles deposited on a carbon black substrate are catalysts commonly employed for the electrooxidation of methanol and carbon monoxide-containing hydrogen feeds [1,. However, improvement of effective electrocatalysts is an essential goal in the development of a practical DMFC. The use of carbon black as a support for noble metals is frequent in the electrodes of polymer membrane electrolyte fuel cells, but the impact of the chemical and physical properties of the carbon on electrocatalytic performance are not yet sufficiently understood. The presence of oxygen surface groups influences the surface behaviour of carbons to a considerable extent . As examples, the wettability and adsorptive behaviour of a carbon, as well as its catalytic and electrical properties, are influenced by the nature and extent of such surface groups. The varying role of oxygenated functionalities on the formation of the dispersed platinum has been established [5-8], but not with an additional metal such as ruthenium. In the present investigation we report how the performance in methanol electrooxidation of PtRu nanoparticles deposited on a carbon black substrate, previously functionalized with oxygen surface groups, is improved.
Journal of Nanomaterials, 2015
PtRu bimetallic nanoparticles were successfully synthesized on polyethyleneimine-(PEI-) functionalized multiwalled carbon nanotubes (MWCNTs) via an effective and facile polyol reduction approach. Noncovalent surface modification of MWCNTs with PEI was confirmed by FTIR and zeta potential measurements. The morphology, crystalline structure, and composition of the hybrid material were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX), respectively. According to SEM and TEM observations, PtRu nanoparticles with narrow size distribution were homogeneously deposited on PEI-MWCNTs. Cyclic voltammetry tests demonstrated that the as-prepared PtRu/PEI-MWCNTs nanocomposite had a large electrochemical surface area and exhibited enhanced electrocatalytic activity towards methanol oxidation in comparison with oxidized MWCNTs as catalyst support. PEIfunctionalized CNTs, as useful building blocks for the assembly of Pt-based electrocatalyst, may have great potential for applications such as direct methanol fuel cell (DMFC).
Applied Catalysis B: Environmental, 2008
In this study, a carbon nanotube-supported PtRu electrocatalyst (PtRuCNT) was prepared, characterized and investigated for methanol electro-oxidation by catalytic activity enhancement using an electrochemical treatment. From XPS analyses, the as-prepared catalyst was found to mainly composed of Pt(0)/Pt(II) states for the Pt element and Ru(0)/Ru(IV) states for the Ru element. When the electrocatalyst was subjected to an enhancement treatment, the Ru(IV) state increased substantially from 29.50% to 44.11%. Both CO-stripping experiments and open-circuit cell voltage measurements indicated that the treated PtRuCNT has given rise to an improved performance on methanol electrooxidation caused mainly by the increase of the Ru(IV) state in this particular case. The single-cell test also revealed that a direct methanol fuel cell (DMFC) can be put into its full operation in a short time. A direct application of this finding is to significantly shorten the activation time of a new DMFC stack. However, the electrochemically treated PtRuCNT catalyst still needs a continuous enhancement mechanism to sustain its enhanced activity. A promotional model is proposed to explain the phenomenon observed and a remedial approach is also suggested to solve the problem for practical applications. ß
Applied Catalysis B: Environmental, 2014
Carbon-supported PtPdCo/C ternary electrocatalysts were prepared by using the sodium borohydride method for use as a cathode catalyst in direct methanol fuel cells (DMFCs). The electrocatalyst particles with a size of 2-3 nm were uniformly dispersed on carbon supports. PtPdCo/C showed a similar performance compared to commercial Pt/C in the oxygen reduction reaction (ORR) tests conducted with a rotating disk electrode (RDE). On the other hand, PtPdCo/C showed higher methanol tolerance than Pt/C in acidic media with methanol. In the single-cell tests, the performance of the PtPdCo/C electrocatalyst was approximately 50% higher than that of Pt/C owing to its enhanced methanol tolerance. In the longterm operation test with the single-cell, the maximum power density of PtPdCo/C decreased only by 14% from its initial value. These results indicate that the PtPdCo/C catalyst is potentially an alternative electrocatalyst for the cathode in DMFCs.
Development of a carbon paper-supported Pd catalyst for PEMFC application
International Journal of Hydrogen Energy, 2012
An oxygen diffusion cathode for a PEMFC has been prepared by directly depositing the catalyst (pure Pd) on a carbon paper support containing 5% of PTFE through an electroless deposition method. A very low-Pd loading of 0.04 mg Pd cm À2 and a higher one, containing 0.22 mg Pd cm À2 , were obtained. Two different experimental approaches were used to evaluate their catalytic activity towards the oxygen reduction reaction. The overall results revealed that the prepared catalysts exhibit a high catalytic activity, but a low efficiency on the catalyst utilization. PEMFC tests, carried out in a single cell, showed the feasibility of using the novel procedure on the preparation of oxygen diffusion cathodes, and its similar performance to a conventional one prepared by spraying the catalyst ink (Pt black) on a carbon paper support.
Methanol-Tolerant Heterogeneous PdCo@PdPt/C Electrocatalyst for the Oxygen Reduction Reaction
Fuel Cells, 2010
We have prepared carbon-supported nanoparticles with the heterogeneous structure of a PdPt shell on a PdCo core which are effective for the oxygen reduction reaction (ORR) in the presence of methanol. The preparation was based on the galvanic replacement reaction between PdCo/C nanoparticles and PtCl 4 2-, a method of general utility which can be extended to the preparation of other core-shell electrocatalysts. The heterogeneous PdCo-core and PtPd-shell architecture was confirmed by multiple techniques including high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, powder X-ray diffraction and X-ray photoelectron spectroscopy. The activity of the PdCo@PdPt/C catalyst in ORR was evaluated in acidic solutions both with and without methanol (0.1 M). The results showed four to sixfold increases in activity over a standard Pt/C catalyst with no apparent loss of catalyst stability. It is inferred that the strain effect from the lattice mismatch between the shell and core components is the major contributor for the enhancement of ORR activity and selectivity.
Applied Nanoscience, 2012
A microwave reduction route was employed for the synthesis of Pt nanoparticles supported on multi-walled carbon nanotubes (MWCNT). The as-prepared Pt-MWCNT electrocatalysts were characterized by FT-IR, XRD and TEM analysis. Further, the as-prepared catalysts were probed for its electrocatalytic activity towards methanol oxidation by cyclic voltammetry (CV) in 0.5 M CH 3 OH ? 0.5 M H 2 SO 4 solution. Two kinds of electrocatalysts viz. Pt-MWCNT and Pt-MWCNT/PANI were probed to study the effect of both carbon nanotubes and polyaniline (PANI) towards methanol oxidation. The effect of scan rate, concentration and long-term cycle stability analysis has been investigated in detail. Results show that the presence of MWCNT and PANI improves the electrocatalytic efficiency towards methanol oxidation. Pt-MWCNT/PANI shows high peak current density towards methanol oxidation and good long-term stability even after 600 cycles indicating that the catalyst could be used for practical applications.