Abstract
Formic acid oxidation was studied on two Pt-Bi catalysts, Pt2Bi and polycrystalline Pt modified by irreversible adsorbed Bi (Pt/Biirr) in order to establish the difference between the effects of Biirr and Bi in 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. SCE (under steady state conditions) improved up to two order of magnitude. The origin of Pt2Bi high activity and stability is increased selectivity toward formic acid dehydrogenation caused by the ensemble and electronic effect and suppression of Bi leaching from the surface during formic acid oxidation. However, although Pt/Biirr also shows remarkable initial activity compared to pure Pt, dissolution of Bi is not suppressed and the poisoning of the electrode surface induced by dehydration path is 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, contributes earlier start of the reaction, while the maximum current density is determined by the ensemble effect.
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