Surface Acid–Base Properties of Anion-Adsorbed Species at Pt(111) Electrode Surfaces in Contact with CO2-Containing Perchloric Acid Solutions

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. Support from MINECO (Spain) through project CTQ2013-44083-P is greatly acknowledged. RMH thankfully acknowledges support from Generalitat Valenciana under the Santiago Grisolía Program (GRISOLIA/2013/008).