Cylindrical carbon fiber microelectrode coated with a silver layer electrodeposited from silver nitrate solution containing Pluronic F127, a surface active agent, and also a Nafion layer prepared using a dip-dry method forms a sensitive, selective and stable amperometric hydrogen peroxide sensor, operating in the cathodic region of potential. The layer formed at the electrode is composed of porous, partially crystalline silver deposits with a significant fraction of attached silver nanoparticles. Using amperometry in stirred solution at 0 mV (vs. Ag/AgCl), the electrode is capable to monitor hydrogen peroxide over its wide concentration range (1 x 10(-5) up to 0.1 M). The response of the electrode is sufficiently time-stable to enable the monitoring of hydrogen peroxide heterogeneous decomposition over manganese dioxide catalyst including the conditions where higher decomposition rates are observed, impossible to be monitored using batch titration. (C) 2010 Elsevier B.V. All rights reserved.