Platinum (Pt) catalyst-coated membranes (CCMs) were prepared using controllable, low-cost, and low-energy-consumption electroless deposition methods and is considered as a catalyst electrolyte for proton exchange membrane fuel cells. The influence of experimental conditions such as temperature,, duration of absorption and reduction processes, type of solvent, pH of reaction, and ethylenediamine (EDA) as a modifier, on the structural, physicochemical, and electrochemical characteristics of CCMs were investigated for this method. The morphological analyses reveal that the smallest Pt nanoparticles (7.8 nm) were formed at 40 degrees C, pH 14, and by means of EDA. This sample appeared to have the highest ionic conductivity, water uptake (WU), and capacitive characteristics. Cation acceptation was observed for the first time by modifying the surface of Nafion with EDA. The electrochemical active surface area for optimum CCM was 7.85 m(2) g(-1), and the current density obtained at 0.5 V was 750 mA cm(-2).