Carbonate and bicarbonate adsorption on Pt(111) electrodes from CO2-saturated acidic solutions is investigated by cyclic voltammetry and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). Spectroscopic results show carbonate and bicarbonate adsorption even at pH = 1, where bulk concentration of these anions is negligible. Moreover, analysis of the potential dependence of band intensities corresponding to adsorbed carbonate and bicarbonate reveals an effect of the electrode potential on the surface acid–base equilibrium. In this regard, increasing potentials favor bicarbonate deprotonation, leading to carbonate formation. A tentative thermodynamic analysis is given to rationalize these trends.