Electrocatalytic properties of Pt-Bi electrodes towards the electro-oxidation of formic acid

Formic acid oxidation was studied on two Pt-Bi catalysts, i.e., Pt2Bi and polycrystalline Pt modified by irreversible adsorbed Bi (Pt/Bi-irr) in order to establish the difference between the effects of Bi-irr and Bi in the alloyed state. The results were compared to pure Pt. It was found that both bimetallic catalysts were more active than Pt with the onset potentials shifted to more negative values and the currents at 0.0 V vs. saturated calomel electrode (under steady state conditions) improved by up to two order of magnitude. The origin of the high activity and stability of Pt2Bi was increased selectivity toward formic acid dehydrogenation caused by the ensemble and electronic effects and suppression of Bi leaching from the surface during formic acid oxidation. However, although Pt/Bi-irr. also showed remarkable initial activity compared to pure Pt, dissolution of Bi was not suppressed and poisoning of the electrode surface induced by the dehydration path was observed. Comparison of the initial quasi-steady state and potentiodynamic results obtained for these two Pt Bi catalysts revealed that the electronic effect, existing only in the alloy, contributed to the earlier start of the reaction, while the maximum current density was determined by the ensemble effect.