Relative Humidity Effect on Anode Durability in PEMFC Startup/Shutdown Processes

Abstract

Ru dissolution and crossover to the cathode from PtRu anode catalysts, which are commonly used in polymer electrolyte membrane fuel cells (PEMFCs) to provide CO tolerance for reformate-based fuel cell applications, have been previously identified as critical durability issues. In this investigation, the effect of relative humidity (RH) on Ru dissolution and crossover was studied using an anode accelerated stress test (AST) to mimic anode potential variation that occur during fuel cell start-ups and shut-downs. Stress testing at lower RH resulted in less Ru degradation, which was indicated by changes in cyclic voltammetry (CV), namely CO stripping peak shifts. The relative degree of Ru crossover was also reflected by the decreases in cell performance and CO tolerance. The results highlight the critical role of water in the Ru degradation mechanism and indicate that controlling the RH could be an effective strategy to mitigate Ru crossover.