Abstract
Proton exchange membrane fuel cells (PEMFCs) have emerged as important zero-emission power sources due to their efficiency and eco-friendly characteristics. A critical feature required for their widespread adoption is the performance of low-temperature cold start. However, at subzero degrees Celsius, the freezing of the produced water can hinder or even lead to failure of the fuel cell start-up process. To successfully achieve a cold start under such conditions, the PEMFC must rapidly and reliably transition from a fully cooled state to a stable operating condition. Various improvements have been focused on the system engineering aspect to address this challenge, yet many of these methods come with their drawbacks. This paper reviews the recent progress of the PEMFC cold start from the perspective of key materials engineering. It provides a detailed summary of how the proton exchange membrane (PEM), catalyst layer, microporous layer (MPL), and gas diffusion layer (GDL) affect the cold-start performance. Further analysis reveals that the fundamental mechanisms of improving cold-start performance can be summarized into three aspects: increasing the ratio of water bound in the ionomer, hindering the transformation process from supercooled water to ice, improving the removal of supercooled water, or ensuring it is transported to the outside of the membrane electrode assembly (MEA) before it gets frozen. By precisely regulating these key components, it is possible to develop a simple and energy-efficient solution for improving the cold start performance of the PEMFC.