4 samples from 10 % to 30% platinum loading with the same carbon support (all Vulcan XC-72) has been synthesized and characterized to be used as electrocatalysts for PEM fuel cells. Adsorption polyol proved to be the most promising synthesis technique among others applied. Conventional and modified polyol methods and impregnation were also utilized to synthesize Pt/C samples. Transmission Electron Microscopy has been used to produce electron microscopic images of the Pt nanoparticles dispersed inside the carbon structure. Furthermore electrochemical characterizations including regular CVs and CO stripping voltammetry were applied to understand and determine the electrochemical performance, while CO stripping voltammetry as an extremely strong tool to detect aggregates in the catalysts samples has been used to examine the presence of agglomerations. In-situ electrochemical studies also have been performed on the electrocatalysts inside a PEM fuel cell system. Cyclic voltammetry, current potential curves (polarization curves) have been used to study the electrochemical performance of the synthesized catalysts. In this regard, the catalysts have been utilized to produce MEAs using a spray technique and different pressing steps and the MEAs were mounted inside the fuel cell test station. At the end to obtain a strong idea on how durable the synthesized catalysts - made by different synthesis techniques- are, the samples underwent a degradation protocol consisting of 100 cycles between certain potentials and all in-situ tests would be repeating to have the data before and after the degradation.