The Effects of Conducting Polymers on Formic Acid Oxidation at Pt Nanoparticles

• The activity of Pt nanoparticles for formic acid oxidation varies with the chemical structure of the polymer support.
• Polycarbazole is strongly activating while a polypyrrole support inhibits formic acid oxidation.
• There is a correlation between activity and the energy of the lowest unoccupied orbital of the repeat unit of the polymer.
• An electronic effect involving electron donation from Pt to the polymer may be responsible for the differences in activity.

The effects of polyaniline, polypyrrole, polyindole and polycarbazole on formic acid oxidation at Pt nanoparticles are compared. The observed trend in activity (polypyrrole < polyaniline ∼ polyindole < polycarbazole) correlates with the decreasing LUMO energies of the monomers (pyrrole > aniline > indole > carbazole), supporting previous evidence of electron donation from Pt nanoparticles into the π-system of a polycarbazole support layer. Density functional theory calculations on CO and carbazole binding to Pt4 clusters show that the electronic effect of carbazole in a carbazole-Pt4-CO ensemble considerably weakens the binding of CO. The magnitude of this effect is comparable to the effects of graphite and graphene supports reported by other researchers, and stronger than the effect calculated here for indole.