Cold start degradation of proton exchange membrane fuel cell: Dynamic and mechanism

Improving the durability of cold start is essential for commercializing proton exchange membrane fuel cells (PEMFCs). This study focuses on the degradation mechanism of cold start. For the first time, through applying segmented print circuit board technology and local characterizations, the degradation behavior of cold start is analyzed in combination with the dynamic response during cold start. The degradation mechanism is built from macroscopic to microscopic. The results show that cell performance and uniformity of the current density distribution are severely degraded after 30 cold start failures. Local current density tests exhibit that during failed cold start, the current is first generated downstream of the cathode. Most of the current is generated before the failing of the cold start, suggesting non-uniform in-plane ice distribution in the catalyst layer. Local electrochemical and physical characterization in the downstream, middle and upstream regions demonstrate the most serious degradation in the downstream region. In contrast, there is a slight degradation in the middle and upstream regions, illustrating the non-uniform degradation distribution during failed cold start. Meanwhile, local physical characterization indicates that freezing-induced crack formation, Pt particle growth, and ionomer agglomeration in the catalyst layer are the root causes of the freezing damage. Through comprehensive characterization, the degradation mechanism of cold start is investigated more profoundly, which is conducive to understanding the cold start process.