Effect of W on PtSn/C catalysts for ethanol electrooxidation

Abstract

Binary and ternary Pt-based catalysts were prepared by the Pechini-Adams modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by TEM and XRD. XRD showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/W and Pt/Sn. Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5 mol dm -3 H 2 SO 4 ) and in the presence of ethanol. The results obtained at room temperature showed that the PtSnW/C catalyst display better catalytic activity for ethanol oxidation compared to PtW/C catalyst. The reaction products (acetaldehyde, acetic acid and carbon dioxide) were analyzed by HPLC and identified by in situ infrared reflectance spectroscopy. The latter technique also allowed identification of the intermediate and adsorbed species. The presence of linearly adsorbed CO and CO 2 indicated that the cleavage of the C-C bond in the ethanol substrate occurred during the oxidation process. At 90°C, the Pt 85 Sn 8 W 7 /C catalyst gave higher current and power performances as anode material in a direct ethanol fuel cell (DEFC).

Development of plurimetallic electrocatalysts prepared by decomposition of polymeric precursors for EtOH/O2 fuel cell

“…For comparison with other electrocatalysts prepared by the same method, the (220) reflection plane was chosen. It can be noticed that the crystallite size of the Pt-M nanocatalysts prepared here are in the same order of magnitude as others reported recently by one of us, e.g., PtSnW/C -7.8 nm, 8 PtSnIr/C -8 nm, 34 PtRuSn/C -5.1 nm, 9 and PtSnNi/C -5.1 nm. 25 Smaller crystallite sizes can be obtained for similar metallic compositions when the preparation method is changed.…”

“…9 The fact that Pt 73 Ni 27 /C and Pt 64 Sn 15 Ru 13 Ni 8 /C favored acetaldehyde formation confirms that the presence of Sn and Ni promotes increased yields of acetaldehyde. 25 The low consumption of ethanol observed for the quaternary catalyst is in contrast with other electrochemical data, published in the literature, 6,8,9,23,25 and can be assigned to the heterogeneous distribution of the metals on the surface of the nanoelectrocatalyst. The nanoparticles can dissolve and recristalize which contributes to inhindance their activity under drastic conditions.…”

“…Although the values reported for the DPP method are higher than the ones described in the literature, several studies have demonstrated that rearrangement of the nanoparticles might occur during operation under fuel cell conditions (high temperature and pressure). 8,34 Electrochemical measurements Figure 2A illustrates some representative cyclic voltammograms obtained for the nanoelectrocatalysts prepared by the DPP method in 0.05 mol L -1 H 2 SO 4 . The region comprised between 0.05 and 0.40 V vs. RHE is characteristic of hydrogen adsorption/desorption at Pt sites.…”

“…Moreover, addition of Ru and Sn to Pt has been found to improve the ethanol oxidation rate. 8 Almeida et al 25 have shown that addition of Ni to PtSn/C catalysts prepared by the DPP method significantly decrease the onset potential of ethanol and CO oxidation, because of a combination between the electronic effect of this metal and the bifunctional effect of Sn. These ternary catalysts were not able to cleave the C−C bond, so the main product was acetaldehyde again.…”

“…30 mW cm -2 ). 3,8,34 Comparing absolute power density values among laboratories is a difficult task, but the results presented in Figure 4 which were obtained in the same experimental conditions, 563 Vol. 23, No.…”