Platinum nanoparticles spontaneously formed on glassy carbon substrates

Platinum nanoparticles (Pt NPs) can be obtained successfully on glassy carbon (GC) substrates by spontaneous deposition taking place upon immersion of the GC electrode, at open circuit, in a 1 mM H₂PtCl₆ + 0.5 M H₂SO₄ solution. The metallic deposits were characterized by ex situ atomic force microscopy (AFM) and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) analysis. At long immersion times, AFM and SEM images show hemispherical Pt NPs of varying sizes (20–390 nm), and heights (50–185 nm), distributed mainly on the GC polishing lines. These deposits coexist with larger Pt clusters, including dendritic structures with sizes in the order of several micrometers, suggesting that both primary and secondary nucleation processes occur on the carbon surface. EDX spectrum confirmed that Pt indeed composes both types of deposits. Cyclic voltammetry was used to evaluate their catalytic activity, qualitatively, towards the hydrogen evolution reaction (HER). The voltammetric response of the GC electrode modified with Pt NPs generated at long immersion times evidenced a behavior similar to that of polycrystalline Pt electrodes, and an enhancement in the catalytic activity regarding HER.