Robust Operation of Fuel Cell Systems in Subfreezing Conditions: A Material-Based Solution to Achieve Better Anode Durability

Automotive fuel cells can suffer from cell voltage reversals because of hydrogen fuel starvation at the anode, which can be exacerbated by subfreezing temperatures because of extensive ice formation and its blockage of the hydrogen supply channels. Here we report on low-temperature (-15 to 45 degrees C) reversal degradation due to hydrogen starvation and evaluate the use of a reversal-tolerant anode (RTA) with an oxygen evolution reaction (OER) catalyst (e.g., iridium oxide). During subfreezing cell reversal, we observed a water electrolysis cell voltage plateau, but the typically subsequent voltage plateau for carbon corrosion usually seen at high temperatures was not found. Repeated cell-reversal tests at subfreezing temperature shows a much slower degradation rate compared with that of high-temperature reversals. A series of isothermal reversal tests at different temperatures indicate that the degradation rate related with carbon corrosion is temperature dependent. As for the effect of RTA on the cell-reversal behavior, we found at subfreezing temperatures that the voltage reversal duration time of the MEA with RTA is similar to that of the MEA without RTA. However, once the cell temperature was sufficiently above freezing, such as during the heating of the startup process, the MEA with RTA would facilitate water electrolysis reactions by consuming water and delaying the onset of carbon corrosion. Thus, our results show that cell reversal with subfreezing internal temperatures does not substantially degrade the anode by carbon corrosion, but rather, the findings show that as the cell warms, an RTA is one approach to extend the survival of the fuel cell stack.