Influence of the electrolyte concentration on the size and shape of platinum nanoparticles synthesized by cathodic corrosion

Cathodic corrosion of platinum in aqueous solutions of NaOH has been studied. Under DC cathodic polarization in concentrations between 0.5 and 10 molar platinum electrode shows corrosion, and above 10 molar it rapidly and efficiently disperses into a suspension of metallic nanoparticles. By applying AC voltage we were able to achieve the efficient dispersion in all concentrations between 0.075 and 20 molar. The size of the resulting nanoparticles has been analyzed both by X-ray diffraction and electrochemical surface area characterization. A clear dependence on concentration was found, paving the way for the size-controlled cathodic synthesis of platinum nanoparticles. The Faradaic efficiency of the cathodic corrosion process was observed to increase with electrolyte concentration, reaching 5% for concentrated NaOH. A sharp increase in the efficiency vs. concentration rate is observed above 1 molar, along with an apparent change in the surface termination of the resulting nanoparticles as seen from voltammetry. As a possible cause a change in the precursor to the nanoparticles is suggested.