Formic acid (FA) oxidation has been investigated at Pt nanopartides (Pt NP) supported on unmodified and polycarbazole (PCZ)-modified glassy carbon (GC) electrodes in sulfuric acid solution. Cyclic voltammetry, scanning electron microscopy, and impedance spectroscopy were used to characterize the PCZ films, whereby similar electrochemical properties and somewhat different morphologies were obtained for GC/PCZ electrodes prepared with various deposition times. These films were drop coated with preformed Pt NP. It was found that while the indirect oxidation of FA was dominant at Pt NP deposited directly on GC, the presence of a PCZ film of similar to 10 nm thickness caused the reaction to proceed predominantly via direct oxidation. Consequently, currents for formic acid oxidation at the low potentials relevant to direct formic acid fuel cell operation were much higher. For example at 0 V vs. SCE, the current was 29 times higher at a GC/PCZ/Pt electrode than at GC/Pt. Furthermore, by varying the thickness of the PCZ layer it was shown that the resistance of the PCZ severely impedes formic acid oxidation when the Pt NP are not in close proximity to the GC surface. (C) 2013 Elsevier Ltd. All rights reserved.