Cathode electrocatalysts measurement

A typical example includes the yttria-stabilized-zirconia-based high-temperature potentiometric oxygen sensor which is widely used in automotive applications. Platinum thick films are applied, forming both the cathode and anode of the sensor. The thick electrode has a porous structure which provides a larger electrode surface area compared to non-porous structures. For current measurement, a porous electrode is desirable since it leads to a larger current output. If the metallic film serves as the electrocatalyst, a porous structure is also desirable, for it provides more catalytic active sites. On the other hand, electrodes formed by the thick-film technique do not have an exact, identical... 

Figure 20.5. Comparison of hydrogen/air polarization curves for spray-based and conventional electrocatalysts at 0. 2 mgPt/cm cathode loadings anode catalyst is identical at 0.05 mgPt/cm. Single 50 cm cell PEM MEA performance measured at 50 °C and atmospheric pressure at constant flow, corresponding to stoichiometry of 1.2 for hydrogen and 2.2 for air at 1 A/cm, and with 100% humidification of the gases, Nafion 112 membrane. (Reproduced with permission of Cabot Corporation.)...

Thus, the EASA firom the voltammogram shown in Fig. 17.7 is 19 m Pt/g Pt, but catalyst loading of cathode cannot be revealed due to proprietary data. Lobato et al. [63] has shown an EASA for commercial HT-PEMFC electrocatalysts between 40 and 55 m Pt/g Pt although scan rate, gas flow rates, and measuring temperature are different to those used to carry out the CV in Fig. 17.7. So comparison of results cannot be done. EASA data between 7 and 20 m Pt/g Pt for an HT-PEM ME A have been shown by Galbiati et al. [29]. In this case, the data may be more comparable with the one presented here but different parameters have been selected to perform the CV. For example, inert gas flow rates have a high impact on accurate determination of the EASA as reported Schneider et al. [64]. 

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