Oxygen Reduction Activity Indicator for Fuel Cell Catalysts at Rated Voltage

Abstract

The available indicators of catalysts for oxygen reduction reaction (ORR) activity are typically characterized at high potentials (commonly at 0.9 V), whereas fuel cells generally operate at 0.8V∼0.6V in its practical application. In our work, charge-transfer resistance (Rct) was proposed to evaluate the ORR activity of catalysts for fuel cells at rated voltage. Firstly, the Rct of MEA with Pt/C catalysts was measured in the range of 0.68V∼0.92V. Tafel slopes calculated from Rct were approximately 80 mV/decade at high potentials, whereas the value increased with the decline of potentials below 0.8 V. It showed that Rct as the ORR indicator of catalysts has certain rationality preliminarily. Secondly, the Rct of MEA with PtxCoy/C catalysts was compared with Pt/C catalysts. It was lower than that of Pt/C in the high potential region, indicating that the higher ORR activities than that of Pt/C catalysts in higher potential region. Whereas they tended to be the same in the low potential region, indicating that the same ORR activities in rated potential region. Thirdly, Rct of MEA with Pt/C catalysts during durability test was monitored. It was interesting that the Rct increased by nearly 125.6% after 900 hours.