nanoparticle: 6 nm Pt tetrahedron surface: clean graphite film: Nafion (15-mer with EW=1144) water content: λ = 3 H2O/HSO3 separation distance: moderate dark gray = CF2 of Nafion and C of graphite white = H beige = S red = O of water and Nafion pale pink = O of hydronium ion light gray = Pt