RAFAEL NOGUEIRA BONIFÁCIO
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Artigo IPEN-doc 17394 High performance carbon supported palladium catalyst in anodes of proton exchange membrane fuel cell2013 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELOCarbon support palladium catalyst (Pd/C) were prepared by borohydride method and characterized by XRD, TEM and EDX and then used to prepare anodes and cathodes for performance evaluation in single cell. For comparison were also used anodes and cathodes prepared with the commercial platinum catalyst (Pt/C), which allowed verifying the efficiency of using Pd/C in cathodes, anodes or both electrodes. It was found similar performance at room temperature, even at the cathode; however, the temperature rise was kinetically favorable to oxygen reduction reaction of cathodes with Pt/C which was not observed for Pd/C cathodes. Moreover, Pd/C anodes showed maximum performance of 83 % related to Pt/C at 85 °C, a behavior that was virtually constant at all temperatures studied and that justifies the application of palladium on fuel cell anodes to platinum replacement on the cost and nature reserves perspectives. The characterization confirmed the palladium FCC crystal structure, a mean particle size of 4.4 nm, presence of some agglomerates and the synthesis method efficiency that resulted in metallic loading of 19.88 % for a nominal load of 20.0 %. The performance achieved by the standards used in MEAs preparation at IPEN and the standards evaluation adopted resulted in a performance higher than reported in the literature motivating this publication.Artigo IPEN-doc 19047 Current density maximization in palladium-based gas diffusion electrode in proton exchange membrane fuel cell2013 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELOIn this study the influence of polymeric ionomer concentration on the performance of gas diffusion electrode containing Pd/C as a substitute for usual Pt/C electrodes in PEMFC was verified. Values between 56 and 59 % of ionomer related to the mass of the catalyst layer resulted in the highest current densities. It was found that the optimum value was strongly dependent on the work potential and temperature. Current density values of 214 mA.cm-2 were obtained at 500 mV, 85 °C and 1 atm for MEAs with Pd/C on both electrodes of PEMFC. With commercial Pt/C only on the cathode side, a value of 745 mA.cm-2 was reached. For comparison, platinum anodes running under the same conditions showed only 13.9 % higher performance than palladium, indicating that improvements in the synthesis method can enhance the performance for palladium getting to be similar to platinum on the hydrogen oxidation reaction. Indeed, these results proved that, from an economic point of view, it is feasible to apply palladium on anodes to replace platinum, although an adequate assessment of durability is still to be investigated.