PtSn/C catalysts

Figure 8.9 Polarization curves for a PtSn/C catalyst recorded by a rotating disk electrode in 0.5 M H2SO4 saturated with either pure hydrogen, a H2/2% CO mixture, and pure CO (the arrow points to the onset of CO oxidation) at 60 °C with 1 mV/s and 2500 rev/min the dashed curve is the cyclic voltammogram (in arbitrary units) in an argon-purged solution at 60 °C with 50 mV/s. (Reprinted with permission from Aienz etal. [2005]. Copyright 2005. Elsevier.)...

In this chapter, two carbon-supported PtSn catalysts with core-shell nanostructure were designed and prepared to explore the effect of the nanostructure of PtSn nanoparticles on the performance of ethanol electro-oxidation. The physical (XRD, TEM, EDX, XPS) characterization was carried out to clarify the microstructure, the composition, and the chemical environment of nanoparticles. The electrochemical characterization, including cyclic voltammetry, chronoamperometry, of the two PtSn/C catalysts was conducted to characterize the electrochemical activities to ethanol oxidation. Finally, the performances of DEFCs with PtSn/C anode catalysts were tested. The microstmc-ture and composition of PtSn catalysts were correlated with their performance for ethanol electrooxidation. 

The addition of a third metal function (Ru, In, W) to PtSn/C catalysts has been reported to increase COg selectivity and/or improve the performance of ethanol electrooxidation in a single cell 133.155-160 context, the incorporation of Rh to the formula-... 

Jiang L, Hsu A, Chu D, Chen R (2010) Ethanol electro-oxidation on Pt/C and PtSn/C catalysts in alkaline and acid solutions. Int J Hydrogen Energy 35(1) 365—372... 

Pt-Sn catalysts only show modest improvement in catalyzing MOR compared to pure Pt catalysts, despite the superior performance of Sn as a co-catalyst to enhance CO oxidation [55-58]. Generally, comparisons between Pt-Ru and Pt-Sn catalysts indicate that the former are more active for the MOR, so that the performance of DMFCs with Pt-Ru/C anode catalysts is substantially better compared to that with PtSn/C catalysts under similar operating conditions [58-62]. 

Regarding the co-catalytic role of Sn for methanol oxidation, on the other hand, the experimental evidence is less conclusive compared to the case of CO oxidation. Colmati et al. prepared PtSn/C catalyst formulations (9 1 and 3 1 atomic ratio) using formic acid reduction and compared the activity with commercial (E-TEK Inc.) Pt/C and PtSn (3 1)/C, including DMFC foel cell experiments [79]. Unfortunately, no comparison with PtRu was presented. Employing 0.4 mg cm anode catalyst load and 3 atm O2 pressure, the maximum fuel cell power output at 343 K was obtained with PtSn (3 1) produced by the formic acid method, 400 mW... 

In the case of PtSn catalysts, no evidence of a ligand effect was observed from an in situ FTIR study on Pt3Sn(l 10) bulk alloy and PtSn nanoparticles supported on carbon. It was proposed that the bifunctional mechaiusm was mainly involved in the oxidation process. The fact that the transition from positive to negative Stark shift of infrared v(CO) frequency during CO oxidation was much more pronoimced on a PtSn/C catalyst than on the Pt/C catalyst was interpreted in terms of the different ways in which OHads (necessary to oxidize CO) nucleates on each catalyst. 

J. Ribeiro, D. dos Anjos, J. Leger, F. Hahn, P. OUvi, A. de Andrade, G. Tremihosi-Filho, K. Kokoh, Effect of W on PtSn/C catalysts for ethanol electrooxidation, J. Appl. Electrochem. 38 (2008) 653-662. 

S. Garda-Rodriguez, S. Rojas, M.A. Pena, J.L.G. Fierro, S. Baranton, J.M. Leger, An FTIR study of Rh-PtSn/C catalysts for ethanol electrooxidation effect of surface composition, Appl. Catal. B Environ. 106 (2011)... 

Ribadeneira and Hoyos [54] have evaluated the catalytic effect of Ni on binary PtSn/C and PtRu/C catalysts. To this end, four different compositions containing nickel were prepared, namely PtRuNi 75 15 10 and 75 10 15 and PtRuNi 75 10 15 and 75 15 10. The addition of Ni to the PtRu/C and PtSn/C catalysts significantly improves their catalytic activities with respect to ethanol electro-oxidation. Bonesi et al. [55] have studied PtSn/C, PtSnNi/C, and PtRuNi/C catalysts prepared by the PVP-Polyol route. The electrochemical characterization of these compositions by chronoamperometry revealed a higher current density for the composition PtSnNi/C, again demonstrating the beneficial effect of the addition of Ni. 

Cunha et al. [56] have investigated the effect of adding Ru to PtSn/C catalysts. The PtSnRu atomic ratios 80 10 10 and 90 05 05 yielded good performance in the electrochemical oxidation of ethanol. The onset of ethanol oxidation occurs near 0.2 V vs. RHE, but product analysis revealed that acetaldehyde was the major product. 

Colmati and co-workers [106] have examined how experimental conditions affect Pt75Sn2s/C catalysts prepared by the formic acid method. Prior to heat treatment, particle sizes of 4.5 nm and experimental compositions close to the nominal one were achieved, but these particles presented low power density, i.e., 20 mW cm" for ethanol oxidation in a PEM-DEFC. Antolini et al. [24] have looked into the effect of introducing ruthenium into PtSn/C catalysts. Again, the desired catalytic composition and homogeneously distribution small particles (3.5 nm) on the carbon support were obtained, but the power density reported for DEFC was relatively low (28mWcm ) for a PEM-DEFC. 

Roman-Martmez, M.C., Cazorla-Amoros, D., Yamashita, EL, and de Miguel, S., and Scelza, O.A. (1999) XAFS study of dried and reduced PtSn/C catalysts nature and structure of the catalytically active phase. Langmuir, 16 (3), 1123-1131. 

Based on the fact that PtiSni/C proved to be a very active anode catalyst for the EOR, additional work has been done to investigate the effect of Pt/Sn atomic ratio [44]. The mean particle size and lattice parameter of the PtSn/C catalyst obtained from XRD patterns and TEM images are summarized in Table 10.4. Figure 10.14 shows the performances of the single fuel cells with different PtSn/... 

In the subsequent research, great endeavor has been made to control the component of PtSn/C catalyst at atomic scale. Now we can obtain a uniform component of PtSn catalyst by modifying the preparation conditions. Figure 10.15 is the HRTEM image and HR-EDS analysis of PtsSn/C nanoparticles. It can be seen... 

Figure 10.14 Performances of single direct ethanol fuel cells with different PtSn/C catalysts as anode catalysts at 90 °C. Anode is PtSn/C with different Pt/Sn atomic ratio (1.33 mg Ptcm ). Solid electrolyte is...

Our primary research indicated that tin oxide could be the active component for ethanol electrooxidation [60,68-70]. Here our focus is to study the effects of the chemical state of tin and the component of PtSn/C catalysts on the performance of DEFCs. For comparison, two PtSn/C catalysts with tin oxide and PtSn alloy were prepared, respectively. For the former, tin oxide with a diameter of 1 nm was prepared first in ethylene glycol, and then platinum was reduced on the surface or near the tin oxide (denoted as PtSn-1). For the latter, first the precursor of Pt and Sn were mixed together, and then they were reduced in FG (denoted as PtSn-2). 

J.C. Serrano-Ruiz, A. Sepulveda-Escribano, F. Rodriguez-Reinoso, Bimetallic PtSn/C catalysts promoted by ceria application in the nonoxidative dehydrogenation of isobutene. J. Catel. 246, 158-165 (2007)... 

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