Similarities and differences between internal short-circuit current and hydrogen crossover current in a proton exchange membrane fuel cell

The proton exchange membrane (PEM) is the core component of PEM fuel cells and plays an important role in isolating gases and electrons during operation; however, PEMs inevitably encounter degradation problems during operation, resulting in weakening or failure of their core functions, thus leading to safety and service life issues. The PEM degradation produces hydrogen crossover and internal short circuit (ISC) currents, which have similar characteristics. Consequently, it is challenging to estimate these two currents and establish a connection between ex situ parameters and actual operation. The safe use of PEM fuel cells requires a distinction between the characteristics of both current types and their generation mechanisms. Our experimental results show that the hydrogen crossover current caused by pinholes during fuel cell operation is influenced by anode overpressure and hydrogen diffuses upon reaching the cathode side of the fuel cell. Meanwhile, the ISC current is influenced by the electrode potential during ex situ testing and fuel cell operation. Compared with the hydrogen crossover current, the efficiency loss due to the ISC current is the "fastest path" because of both currents have different reaction paths. X-ray computed tomography analyses are consistent with the results of the electrochemical tests.