2. Investigation of the Effect of Different Organic Additives on Morphology and Electrocatalytic Activity of Platinum Nanomaterials Towards Oxygen Reduction Reactions

In the present study, different carbon-supported platinum nanomaterials were prepared using electrodeposition method and the influences of some organic additives, such as potassium citrate, Nafion and polyvinylidene fluoride (PVDF) on the morphology, electrochemically active surface area (ESA) and electrocatalytic activity of platinum nanomaterials (Pt/Vulcan XC-72) were evaluated. The materials were electrodeposited on a rotating disk electrode (RDE) from the electrolyte hexachloroplatinic acid (H₂PtCl₆) and H₂SO₄ in the absence and presence of the organic additives. The materials obtained were characterized using powder X-ray diffraction, scanning electron microscopy, electrochemical methods. In addition, the electrocatalytic activity of the materials towards oxygen reduction reactions was evaluated by employing linear sweep voltammetry on RDE at 1000 rpm. The presence of the organic additives increased the overpotential at the growth stage of the particles, leading to a decrease in the particle size and hence an increase in the ESA of platinum nanoparticles from 19 to 43 m²/g(Pt) The electrocatalysts prepared using the different organic additives have the following increasing order of electrochemical activities towards the ORR in an aqueous solution of HClO₄: citrate < without the organic additives < Nafion < PVDF in the potential range of ca. 0.7–0.9 V. This electrochemical behavior can be attributed to the differences in the particle size, ESA, and the morphology of the synthesized carbon-supported platinum nanomaterials.