An optimization study of PtSn/C catalysts applied to direct ethanol fuel cell: Effect of the preparation method on the electrocatalytic activity of the catalysts (original) (raw)
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Journal of Applied Electrochemistry, 2010
Vulcan XC-72R carbon was pretreated using acid and thermal activation methods, and the carbons obtained were used as supports for a PtSn/C catalyst synthesized by a successive reduction process. Surface characteristics of the supports, including BET surface area, pH PZC and functional group, were analyzed using physical N 2 adsorption, mass titration, acid-base titration, and Fourier transform infrared (FTIR) spectrometer technique, respectively. The prepared PtSn/C catalysts were characterized by X-ray diffractometer (XRD), energy dispersive X-ray spectrometer (EDX), inductively coupled plasmaatomic emission spectrometry (ICP-AES), and transmission electron microscope (TEM) techniques, and then were examined for their behavior under ethanol oxidation as well as for their performance in a direct ethanol fuel cell (DEFC). The results showed that pretreatment by HNO 3 produced various oxygenated functional groups on the support surface and increased its acidic property. The strong acidity of the acid-treated support led to an unfavorable condition for the Pt reduction reaction and resulted in low Pt content but high Pt:Sn ratio in the PtSn/C catalyst. On the other hand, thermal activation increased the base functional groups on the carbon surface, which enhanced reduction of Pt precursor, and consequently, provided a small average metal particle size of 2.2 nm. The results from cyclic voltammetry, chronoamperometry and cell performance testing confirmed that the catalytic activity for ethanol oxidation and the performance in the direct ethanol fuel cell of the heat-treated carbon-supported PtSn catalyst was superior to the fresh PtSn/C catalyst and the acid-treated carbon-supported PtSn catalyst.
PtSn/C electrocatalysts prepared by different methods for direct ethanol fuel cell
Studies in Surface Science and Catalysis, 2006
Sn atomic ratios of 50:50 and 90:10 were prepared by alcohol-reduction process, using ethylene glycol as solvent and reducing agent, and by borohydride reduction. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry. The electro-oxidation of ethanol was studied by cyclic voltammetry using the thin porous coating technique. The electrocatalysts performance depends greatly on preparation procedures and Pt:Sn atomic ratios.
PtSnCe/C electrocatalysts for ethanol oxidation: DEFC and FTIR
2011
The ethanol oxidation reaction (EOR) was investigated using PtSnCe/C electrocatalysts in different mass ratios (72:23:5, 68:22:10 and 64:21:15) that were prepared by the polymeric precursor method. Transmission electron microscopy (TEM) showed that the particles ranged in size from approximately 2 to 5 nm. Changes in the net parameters observed for Pt suggest the incorporation of Sn and Ce into the Pt crystalline network with the formation of an alloy between Pt, Sn and/or Ce. Among the PtSnCe catalysts investigated, the 68:22:10 composition showed the highest activity toward ethanol oxidation, and the currentetime curves obtained in the presence of ethanol in acidic media showed a current density 50% higher than that observed for commercial PtSn/C (E-Tek). During the experiments performed on single direct ethanol fuel cells, the power density for the PtSnCe/C 68:22:10 anode was nearly 40% higher than the one obtained using the commercial catalyst. Data from Fourier transform infrared (FTIR) spectroscopy showed that the observed behavior for ethanol oxidation may be explained in terms of a double mechanism. The presence of Sn and Ce seems to favor CO oxidation, since they produce an oxygen-containing species to oxidize acetaldehyde to acetic acid.
PtSnCe/C electrocatalysts for ethanol oxidation: DEFC and FTIR “in-situ” studies
International Journal of Hydrogen Energy, 2011
The ethanol oxidation reaction (EOR) was investigated using PtSnCe/C electrocatalysts in different mass ratios (72:23:5, 68:22:10 and 64:21:15) that were prepared by the polymeric precursor method. Transmission electron microscopy (TEM) showed that the particles ranged in size from approximately 2 to 5 nm. Changes in the net parameters observed for Pt suggest the incorporation of Sn and Ce into the Pt crystalline network with the formation of an alloy between Pt, Sn and/or Ce. Among the PtSnCe catalysts investigated, the 68:22:10 composition showed the highest activity toward ethanol oxidation, and the currentetime curves obtained in the presence of ethanol in acidic media showed a current density 50% higher than that observed for commercial PtSn/C (E-Tek). During the experiments performed on single direct ethanol fuel cells, the power density for the PtSnCe/C 68:22:10 anode was nearly 40% higher than the one obtained using the commercial catalyst. Data from Fourier transform infrared (FTIR) spectroscopy showed that the observed behavior for ethanol oxidation may be explained in terms of a double mechanism. The presence of Sn and Ce seems to favor CO oxidation, since they produce an oxygen-containing species to oxidize acetaldehyde to acetic acid.
Ionics, 2010
PtSn/C electrocatalysts (Pt:Sn atomic ratios of 50:50 and 60:40) were prepared using citric acid as reducing agent, and the pH of the reaction medium was varied by the addition of OH− ions. The obtained electrocatalysts were characterized by energy dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy. The electrocatalysts were tested on the direct ethanol fuel cell (DEFC) at 90 °C. The obtained PtSn/C electrocatalysts showed the presence of a face-centered cubic, Pt, and SnO2 phases. In DEFC studies, the PtSn/C electrocatalysts showed a superior performance compared to a commercial PtSn/C and Pt/C electrocatalysts from E-TEK.
Catalytic Activity of Carbon-Supported Electrocatalysts for Direct Ethanol Fuel Cell Applications
Journal of The Electrochemical Society, 2008
The catalytic activity of some carbon-supported electrocatalysts toward the ethanol oxidation reaction ͑EOR͒ and the oxygen reduction reaction ͑ORR͒ in the presence of ethanol was investigated. It was found that anodes based on PtSn alloys possess a higher catalytic activity for the EOR, compared to other anode catalysts such as Pt, PtRu, and Pt oxide. For example, when tested in a direct ethanol fuel cell, a twofold increase was observed in the current density obtained from a PtSn-Pt membrane electrode assembly ͑MEA͒ configuration at 0.4 V, compared to the current density obtained from a PtRu-Pt MEA. Furthermore, it was found that cathode catalysts based on Ru/C exhibit a good catalytic activity for the ORR and a high selectivity for this reaction in the presence of ethanol. The results showed that in the presence of 0.125, 0.25, or 0.5 M ethanol concentrations, a decrease in the onset potential of about 60, 62, and 68 mV emerged, respectively. These values were about ten times lower than those measured for some Pt-based cathode catalysts tested in this study in the presence of 0.125 M EtOH. Accordingly, an ethanol fuel cell based on a PtSn/C anode and a Ru/C cathode showed important current density vs cell voltage characteristics.
International Journal of Electrochemical Science, 2012
A 20% Pt3Sn/C catalyst was prepared by reduction with formic acid and used in a direct ethanol fuel cell at low temperatures. The electro-catalytic activity of this bimetallic catalyst was compared to that of a commercial 20% Pt/C catalyst. The PtSn catalyst showed better results in the investigated temperature range (30°-70°C). Generally, Sn promotes ethanol oxidation by adsorption of OH species at considerably lower potentials compared to Pt, allowing the occurrence of a bifunctional mechanism. The bimetallic catalyst was physico-chemically characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The presence of SnO2 in the bulk and surface of the catalyst was observed. It appears that SnO2 can enhance the ethanol electro-oxidation activity at low potentials due to the supply of oxygen-containing species for the oxidative removal of CO and CH3CO species adsorbed on adjacent Pt active sites.
Carbon-supported ternary PtSnIr catalysts for direct ethanol fuel cell
Electrochimica Acta, 2007
Binary PtIr, PtSn and ternary PtSnIr electrocatalysts were prepared by the Pechini-Adams modified method on carbon Vulcan XC-72, and these materials were characterized by TEM and XRD. The XRD results showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of solid solutions between the metals Pt/Ir and Pt/Sn. However, the increase in Sn loading promoted phase separation, with the formation of peaks typical of cubic Pt 3 Sn. The electrochemical investigation of these different electrode materials was carried out as a function of the electrocatalyst composition, in a 0.5 mol dm −3 H 2 SO 4 solution, with either the presence or the absence of ethanol. Cyclic voltammetric measurements and chronoamperometric results obtained at room temperature showed that PtSn/C and PtSnIr/C displayed better electrocatalytic activity for ethanol electrooxidation compared to PtIr/C and Pt/C, mainly at low potentials. The oxidation process was also investigated by in situ infrared reflectance spectroscopy, to identify the adsorbed species. Linearly adsorbed CO and CO 2 were found, indicating that the cleavage of the C C bond in the ethanol substrate occurred during the oxidation process. At 90 • C, the Pt 89 Sn 11 /C and Pt 68 Sn 9 Ir 23 /C electrocatalysts displayed higher current and power performances as anode materials in a direct ethanol fuel cell (DEFC).
Ethanol Oxidation Reaction Using PtSn/C+Ce/C Electrocatalysts: Aspects of Ceria Contribution
Electrochimica Acta, 2014
The ethanol oxidation reaction (EOR) was investigated using PtSn/C + Ce/C electrocatalysts in different mass ratios (58:42, 53:47, and 42:58) prepared using the polymeric precursor method. Transmission electron microscopy (TEM) experiments showed particles sizes in the range of 3 to 7 nm. Changes in the net parameters observed for Pt suggest the incorporation of Sn into the Pt crystalline network with the formation of an alloy mixture with the SnO 2 phase. Among the PtSn/C + Ce/C catalysts investigated, the 53:47 composition showed the highest activity towards the EOR. In this case, the j versus t curves obtained in the presence of ethanol in acidic media exhibited a current density 90% higher than that observed with the commercial PtSn/C (ETEK). Correspondingly, during the experiments performed on single direct ethanol fuel cells, the maximum power density obtained using PtSn/C + Ce/C (53:47) as the anode was approximately 60% higher than that obtained using the commercial catalyst. FTIR data showed that the observed behavior for ethanol oxidation may be explained in terms of a synergic effect of bifunctional mechanism with electronic effects, in addition to a chemical effect of ceria that provides oxygen-containing species to oxidize acetaldehyde to acetic acid.