**Figure 2.**

time consuming and expensive methodology for experimental investigations. This chapter also provides information on the modification of Accelerated Stress Test (AST) created for exploring fuel cell degradation behavior and decreasing those restrictions [11].

Different driving behavior corresponds to various PEMFC operating conditions which can lead to numerous cases of PEMFC component degradation. For example, load cycling conditions such as voltage cycling, temperature cycling, and humidity cycling brings about membrane degradation; cracks, pinhole, and peroxide and hydrogen peroxide production [12]. These conditions also result in catalyst degradation such as Ostwald ripening of particles and sintering of particles [12]. If FCEV is driven at start-stop condition, PEMFCs will operate at high voltage, high temperature and low humidity [13, 14]. The detachment of catalyst particles from carbon support, Ostwald ripening of particles, sintering of particles, and dissolution of the catalyst can occur under start-stop circumstances [13, 14]. Evaluating and understanding material degradation and failure mechanisms through physical, chemical, and electrochemical analyses are important for material selection and fuel cell design. In terms of electrochemical analyses, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) are preferable. EIS is applied for diagnosing behavior of PEMFC such as metal corrosion, electrode-electrolyte interface behavior, double-layer capacity, electrical properties of material and interfaces, and electrodeposition [15]. Morphological studies using Scanning Electron Microscopy (SEM) technique, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) technique, and X-ray Photoelectron Spectroscopy (XPS) technique are proposed by scientists and engineers. This chapter presents case studies of material degradation occurring from driving behavior, since the information about the material degradation can be compiled into a database for the improvements of the cell component performance and durability, leading to the creation of new materials and new fuel cell hybridization designs.
