(93e) Physicochemical Characterization of Pd-Based Electrocatalysts for Bioethanol Electrooxidation on FUEL CELLS

Fuel cells are electrochemical devices, which directly converts chemical energy from a reaction into electricity without intermediate transformation processes of heat to mechanical energy. Within the current energy alternatives, the fuel cell working at low temperature with direct bioethanol supply. Nowadays bioethanol electro-oxidation on Pd electrode surfaces has become in one of the most interested processes in electro-catalysis. Due to direct bioethanol fuel cells (DBEFCs) in alkaline media have demand more attention as power devices because of their high energy density [3], fast kinetics, availability and easy handling of bioethanol and the option of using less expensive metal catalysts. The most investigated materials for this proposes are platinum and palladium, and their combinations with tin, nickel and ruthenium. However, Palladium has shown better stability and prices than platinum, with good answers in terms of current and electrochemical active surface.

Electro-catalysts in alkaline media are important for researchers, because of their use it is possible to avoid side effects such a CO poisoning and stability. However, this technology now requires more functional electrocatalysts that facilitate the breaking of the bonds C - C, full oxidation to CO2 and high resistance to deactivation by adsorption of CO. [2].

In this work, are presented results of the synthesis and characterization of Pd-Sn and Pd-Ru nano-particles supported in Carbon Vulcan XC-72. Pd-Sn/C and Pd-Ru/C with 30w% of metal loading were synthetized by polyol reduction using microwave heating, PdCl₂, SnCl₂x2H₂O and RuCl₃ as metallic precursors and Carbon Vulcan XC 72R as supporting material, following the methodology described by Liu on [1]. Structural, chemical, and morphology features of the catalysts were examined by X-Ray Diffraction (XRD) patterns were collected by a Rigaku diffractometer with Cu Ka radiation (λ=1.5406A) scanning 5°/seg  with 20<2θ<90. X-Ray Photoelectron Spectroscopy (XPS) analysis was carried out in Surface Science Instrument SSX-100, scanning 20 times over the surface and Scannig Electron Microscopy (SEM) was done in a LEO 1550 FESEM. Results showed that polyol reduction method with microwave heating reduce very well these metals on carbon. From XRD difractogram is evident that metal nanoparticles are on carbon surface. Metal load on the carbon measured by XPS and molar ratio between them was closer to the theoretical one. SEM images showed that PdRu/C has smaller cluster on carbon surface than PdSn/C, in contrast is PdSn/C who show better dispersion. As a final result, the relationship between physicochemical characteristics and functionality are discussed.

REFERENCES

[1] Z. Liu, L. M. Gan, L. Hong, W. Chen, and J. Y. Lee, “Carbon-supported Pt nanoparticles as catalysts for proton exchange membrane fuel cells,” Journal of Power Sources, vol. 139, no. 1–2, pp. 73–78, Jan. 2005. 

[2] N. J. Robertson, H. A. K. Iv, T. J. Clark, P. F. Mutolo, and G. W. Coates, “Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications,” no. 13, pp. 3400–3404, 2010. 

[3]E. H. Yu, U. Krewer, and K. Scott, “Principles and Materials Aspects of Direct Alkaline Alcohol Fuel Cells,” Energies, vol. 3, no. 8, pp. 1499–1528, Aug. 2010. 

[4] S. a. Grigoriev, P. Millet, and V. N. Fateev, “Evaluation of carbon-supported Pt and Pd nanoparticles for the hydrogen evolution reaction in PEM water electrolysers,” Journal of Power Sources, vol. 177, no. 2, pp. 281–285, Mar. 2008. 

[5] H. Li, G. Sun, L. Cao, L. Jiang, and Q. Xin, “Comparison of different promotion effect of PtRu / C and PtSn / C electrocatalysts for ethanol electro-oxidation,” vol. 52, pp. 6622–6629, 2007.