RAFAEL NOGUEIRA BONIFÁCIO
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Artigo IPEN-doc 20827 Comparative analysis between mass and volume of catalysts as a criterion to determine the optimal quantity of nafion ionomer in catalysts layers2015 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELOStudies 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.Artigo IPEN-doc 20117 Influence of the relative volumes between catalyst and nafion ionomer in the catalyst layer efficiency2014 - BONIFACIO, RAFAEL N.; OLIVEIRA NETO, ALMIR; LINARDI, MARCELOOver 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.