Four novel composite catalysts have been developed by the electrodeposition of Pt onto glassy carbon electrode (GCE) modified with polyindoles: polyindole, poly(5-methoxyindole), poly(5-nitroindole) and poly(5-cyanoindole). As-formed composite catalysts are characterized by SEM. XRD and electrochemical analysis. Compared with Pt nanoparticles, respectively, deposited on the bare GCE and on the GCE modified with polypyrrole, the four newly developed composite catalysts exhibit higher catalytic activity towards formic acid electrooxidation by improving selectivity of the reaction via dehydrogenation pathway and thus mostly suppressing the generation of poisonous COads species. The enhanced performance is proposed to come from the synergetic effect between Pt and polyindoles and the increase of electrochemical active surface area (EASA) of Pt on polyindoles. (C) 2010 Elsevier Ltd. All rights reserved.