(Bi)sulfate adsorption on quasiperfect Pt(111) facets from acidic aqueous electrolytes as monitored by optical techniques

The adsorption of (bi)sulfate on quasiperfect Pt(111) facets was monitored by simultaneous reflectance spectroscopy (RS) and second harmonic generation (SHG) while scanning the potential linearly between prescribed values in aqueous acidic solutions. Simple correlations were found between both the normalized differential reflectance, Delta R/R (lambda = 633 nm, angle of incidence, phi(inc) = 45 degrees) and the intensity of the SHG light, I-pp(2 omega) (lambda(inc) = 590 nm, where pp refers to the input and output polarization) and the Gibbs free excess of (bi)sulfate, Gamma(HSO4)- (Herrero et al. J. Electroanal. Chem. 2002, 534,79-89), in a potential range negative to the sharp voltammetric peak, for (bi)sulfate concentrations spanning over two orders of magnitudes.