a b s t r a c tA novel amperometric sensor based on the incorporation of ruthenium oxide hexacyanoferrate (RuOHCF) into multiwalled carbon nanotubes (MWCNTs) immobilized on a glassy carbon electrode is described. Cyclic voltammetry experiments indicated that the cathodic reduction of hydrogen peroxide at the RuOHCF/MWCNTs100/GC modified electrode is facilitated, occurring at 0.0 V vs. Ag/AgCl/KCl (sat) . Following the optimization of the experimental conditions, the proposed sensor presented excellent analytical properties for hydrogen peroxide determination, with a low limit of detection (4.7 lmol L À1 ), a large dynamic concentration range (0.1-10 mmol L À1 ) and a sensitivity of 1280 lA mmol À1 L cm À2 . The usefulness of the RuOHCF/MWCNTs100/GC electrochemical sensor was confirmed by monitoring the consumption of hydrogen peroxide during the degradation of phenol by the Fenton reaction.