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.
Electrocatalytic properties of Pt-Bi electrodes towards the electrooxidation of formic acid