Durability is mainly affected by the degradation mechanisms related to different catalysts -how and why the catalyst degrades. Degradation of the catalytic layer includes the degradation of Pt-based catalysts. Their degradation results in the reduction of the electrochemically active area, reducing the performance of the fuel cell and making it essential for researchers to keep in mind the mechanisms causing degradation. The degradation of a catalyst can be visualized on a polarization curve since the efficiency of the catalyst will be decreased along with the degradation of the catalyst. This means the kinetics of the catalyst will decrease while decreasing the current-voltage polarization curve by lowering the MSA of the catalyst; hence, the current-voltage polarization curve will curve down after degradation happens on a catalyst. There are mainly three main degradation mechanisms of Pt-based catalysts that are worth investigating: (1) Pt particle agglomeration and growth, (2) Pt loss and migration, and (3) Contamination of active sites caused by impurities. These degradation mechanisms will reduce the active area of the catalyst or increase contact resistance with catalyst support . The degradation mechanisms will be described in further detail in the subsequent sections.