Expulsion of borate ions from the silver/solution interfacial region during underpotential deposition discharge of BiIII in borate buffer

Abstract

Electrochemical quartz crystal microbalance (EQCM) studies of the underpotential deposition (UPD) of bismuth(III) at silver were performed in borate buffers in the pH range 8–10. A bismuth borate species is adsorbed at positive rational potentials. At more negative potentials the adsorbed species is reduced to UPD bismuth(o) and there is a concomitant decrease in electrode mass. The surface reduction process corresponds to the expulsion of four BO^–₂ anions from the interface according to the reaction Bi(BO^–₂)₄+ 3e = Bi_upd+ 4BO^–₂. The EQCM technique has been demonstrated to be well suited to study the mechanism of underpotential deposition of metals and the stoichiometry of adsorbed surface complexes.