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Now showing 1 - 4 of 4
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    Methanol tolerant electrocatalysts for the oxygen reduction reaction
    (Springer, 2015) Asteazaran, Mariano; Bengio, Silvina; Triaca, Walter; Castro Luna, Ana
    Direct methanol fuel cells (DMFCs) represent an interesting alternative in obtaining electricity in a clean and efficient way. Portable power sources are one of the most promising applications of passive DMFCs. One of the requirements in these devices is to use high alcohol concentration, which due to methanol crossover causes a considerable loss of fuel cell efficiency. In order to develop methanol tolerant cathodes with suitable activity, different supported catalysts namely PtCo/C and PtCoRu/C, were prepared either via ethylene glycol reduction (EG) with or without microwave heating assistance (MW) or via the alloy method, the latter followed by a thermal treatment in a reducing atmosphere (N2/H2). All cathode-catalysts were tested to determine the role of the components in simultaneously enhancing the oxygen reduction reaction (ORR) and discouraging the methanol oxidation reaction. According to the synthesis methodology, X-ray photoelectron spectra showed that the amount of metal oxides on the surface varies, being higher on the PtCo/C EG and PtCoRu/C EG catalysts. The electrochemical characterization of the catalysts was accomplished in a three electrodes electrochemical cell with a glassy carbon rotating disk electrode covered with a thin catalytic film as working electrode. To study the ORR and the influence of different methanol concentrations, linear sweep voltammetry and cyclic voltammetry were employed. The PtCo/C EG, with an important metal oxide amount on the surface, and the PtCoRu/C MW and EG electrodes, both with RuO2 on their surfaces, were the most tolerant to methanol presence.
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    Síntesis de nano catalizadores para celdas de combustible de metanol directo
    (Revista Tecnología y Ciencia UTN, 2014) Asteazaran, Mariano; Bonesi, Alejandro; Triaca, Walter; Castro Luna, Ana
    Las celdas de combustible de metano/ directo, DMFCs, permiten una conversión completa de la energía de la reacción química (CH)3OH(ac)+3/2 O2(g)=7CO2(g)+2H2O(l) en energía eléctrica. El platino es el catalizador más utilizado en las DMFCs. Para poder generar cantidades aceptables de corriente no se puede prescindir del uso de este metal como catalizador. Como la catálisis se manifiesta a nivel superficial, si se sintetizan nano partículas catalíticas soportadas sobre negro de carbón se obtendrá una gran área de reacción. El empleo de la nano tecnología y la combinación de Pt con otros metales aumenta la actividad electro catalítica y reduce el costo de las celdas de combustible. Se sintetizan y se determinan las actividades electro catalíticas de nano partículas en base platino como material de electrodo para el cátodo donde se lleva a cabo la reacción de reducción de oxígeno en la DMFC.
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    Research on methanol tolerant catalysts for the oxygen reduction reaction
    (Springer, 2015) Asteazaran, Mariano; Cespedes, German; Bengio, Silvina; Moreno, Mario; Triaca, Walter; Castro Luna, Ana
    Direct methanol fuel cells (DMFCs) generate electricity in a clean and efficient way, so they are a valuable alternative to traditional environmentally harmful technologies. Portable power sources are one of the applications of passive DMFCs. One of the requirements in these devices is the use of high alcohol concentration. Methanol permeation across the polymer electrolyte membrane (methanol crossover) causes a loss of fuel cell efficiency as the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) occur simultaneously at the cathode. To develop methanol-tolerant catalysts with suitable activity, different PtM/C and PtMRu/C combinations with M = Co or Fe were prepared by a modified impregnation method. The synthesized catalysts were studied to determine the role of the components in enhancing the ORR and simultaneously discouraging the MOR. The materials were characterized by TEM, XPS and EDS. Well-distributed particles for all the catalysts were shown by TEM. XPS spectra revealed that the method produces a great amount of metallic Pt. The electrochemical characterization was carried out by linear sweep voltammetry and cyclic voltammetry, in a three-electrode electrochemical cell with a glassy carbon rotating disk electrode covered with a thin catalytic layer and a Nafion film as the working electrode. Binary and ternary catalysts have a good activity for the ORR. However, the enhanced activity of binary catalysts is lost when the ORR is studied in the presence of methanol. Ternary catalysts containing Ru showed higher methanol-tolerance, regardless of the composition.
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    Searching for suitable catalysts for a passive direct methanol fuel cell cathode
    (Elsevier, 2015) Asteazaran, Mariano; Cespedes, German; Moreno, Mario; Bengio, Silvina; Castro Luna, Ana
    Trimetallic PtMRu/C cathode catalysts with M ¼ Co or Fe obtained by an impregnation procedure using ethylene glycol and NaBH4 as reducing agent, with suitable activity for the oxygen reduction reaction (ORR) and improved tolerance to methanol, have been physically characterized by HRTEM, EDS and XPS. The examined nanoparticles have a small particle size and are well spread on the carbon support. Pt is mainly found as Pt(0) and Co, Fe and Ru are mostly oxidized. To study their durability and performance for ORR and methanol tolerance over time, the catalysts were subjected to an electrochemical accelerated stress test (AST), consisting in cycling the potential 2000 times. Polarization curves for ORR with and without methanol were recorded. After the AST the trimetallic PtMRu/C catalysts are able to keep their performance for ORR in the presence of methanol.