Influence of the relative volumes between catalyst and Nafion ionomer in the catalyst layer efficiency

Comparative analysis between mass and volume of catalysts as a criterion to determine the optimal quantity of Nafion ionomer in catalyst layers

“…Recently [83], it was verified that this ionomer quantity (59%NI) is higher than usual because the carbon used as support material in these studies is less dense than the carbon used in the commercial catalyst.…”

“…The TEM analyses were performed on a JEOL 1010 Transmission Electron Microscope, whose operation was limited to 80 keV beam. The images obtained were used to count and estimate the average particle diameters ðÂÞ and to calculate the specific surface areas (SSA) of palladium from the distributions of diameters, according to Equation (1) [70,71,83]. For these procedures, it was counted more than 600 particles of each catalyst.…”

“…The electrodes were then kept in a stove at 80 C for two hours and afterwards were hot pressed to both sides of a Nafion 115 membrane. This procedure was performed by first heating the MEA to between 105 and 125 C and then applying a pressure of 1.000 kgf$cm À2 for 2 min [12,33,83].…”

“…However, the same studies found that changes in the mass of catalyst applied to the electrodes [9] and changes in the ratio between metal and support [8] modified the required masses of Nafion ionomer which resulted in higher performances. On the other hand, a recent study [83] verified that catalyst with the same support material (carbon) and the same metal loading (20%) can present different volumes due to modifications induced by heat treatment in the support material. It was also shown that these different volumes significantly modify the amount of ionomer needed to prepare catalyst layers with high performance, i.e., the formation of triple phase boundaries with high efficiency [83].…”

“…On the other hand, a recent study [83] verified that catalyst with the same support material (carbon) and the same metal loading (20%) can present different volumes due to modifications induced by heat treatment in the support material. It was also shown that these different volumes significantly modify the amount of ionomer needed to prepare catalyst layers with high performance, i.e., the formation of triple phase boundaries with high efficiency [83]. From this conclusion, it is expected that a volumetric criterion should be developed to determine the amount of ionomer to be used in the preparation of catalyst layers for different catalysts in order to make comparisons between them at each one's conditions of greatest efficiency [83].…”