RAFAEL NOGUEIRA BONIFÁCIO

RAFAEL NOGUEIRA BONIFÁCIO

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Comparative analysis between mass and volume of catalysts as a criterion to determine the optimal quantity of nafion ionomer in catalysts layers
2015 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELO
Studies in the proton exchange membrane fuel cell (PEMFC) have evaluated different catalyst systems, using fixed mass percentages as the criterion to prepare catalyst layers. Some studies presented masses between 20 and 40% of ionomer in the catalyst layer as best composition; however, they also showed that any modification in the catalyst structure, such as support material or metal percentage, changes remarkably the membrane electrode assembly (MEA) performances. Thus, the volume of a catalyst used changes the amount of Nafion ionomer required to prepare catalyst layers with high efficiency. Consequently, to compare different catalysts in their highest performance conditions, it has become necessary to develop a volumetric criterion to calculate the quantity of Nafion ionomer necessary for each catalyst. In this work, the masses and the volumes of catalysts were compared to three other catalysts as the criterion to transpose the adjustment of the catalyst layer composition made to Pd/C 20%. The use of catalyst volume as the criterion to calculate the quantity of Nafion ionomer in the catalyst layer resulted in MEAs significantly more efficient than those prepared according to the fixed mass percentage.
Influence of the relative volumes between catalyst and nafion ionomer in the catalyst layer efficiency
2014 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELO
Over the years, studies have analyzed the composition of the catalyst layer using commercial platinum catalyst, supported on Vulcan XC72 with 20% of metal loading (Pt/C 20%Mw), and found that values between 20 and 40% of Nafion ionomer related to the mass of the catalyst layer (% NIW) have resulted in more efficient electrodes for PEMFC. Recent studies with catalysts synthesized on Vulcan XC72 resulted in 59% NIW as the best formulation. In this work, the commercial and the synthesized Pt/C 20%Mw catalyst were evaluated by Gas Pycnometry, Gas Adsorption (through BET and BJH), and Mercury Intrusion Porosimetry. The results showed volumetric differences between the Vulcan XC72 used in commercial catalyst and the Vulcan XC72 commercially available for synthesis (as purchased). These differences impair the synthesized catalyst in comparison with the commercial one. Therefore, the relationship between the quantities of catalysts and Nafion ionomer on the catalyst layers must be calculated as a function of the catalysts volumes.
Catalyst layer optimization by surface tension control during ink formulation of membrane electrode assemblies in proton exchange membrane fuel cell
2011 - BONIFACIO, RAFAEL N.; PASCHOAL, JOSE O.A.; LINARDI, MARCELO; CUENCA, RICARDO
Desenvolvimento de processo de produção de conjuntos eletrodo-membrana-eletrodo para células a combustível baseadas no uso de membrana polimérica condutora de prótons (PEMFC) por impressão a tela
2011 - BONIFACIO, RAFAEL N.; LINARDI, MARCELO; CUENCA, RICARDO
Desenvolvimento de tecnologia para confecção de eletrodos e conjuntos eletrodo-membrana-eletrodo (MEA) por impressão à tela para aplicação em modulos de potência de células PEMFC
2012 - FERNANDES, VALERIA C.; CUNHA, EDGAR F. da; BONIFACIO, RAFAEL N.; DRESCH, MAURO A.; DOUBEK, GUSTAVO; SANTIAGO, ELISABETE I.; LINARDI, MARCELO
High performance carbon supported palladium catalyst in anodes of proton exchange membrane fuel cell
2013 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELO
Carbon 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.
Current density maximization in palladium-based gas diffusion electrode in proton exchange membrane fuel cell
2013 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELO
In 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.