We report a one-pot and environment-friendly sonochemical synthesis of amorphous carbon-supported silver nanoparticles (Ag NPs) using carbon nanodots derived from biomass, as a combined reducing and capping agent. The as-prepared amorphous carbon-supported silver nanoparticles (Ag/C nanocomposites) exhibited excellent catalytic activity toward electrocatalytic reduction of hydrogen peroxide (H2O2). Moreover, the Ag/C modified glassy carbon electrode showed a good sensing ability with high sensitivity and low detection limit serving as a nonenzymatic H2O2 sensor. This facile approach to synthesize amorphous carbon-supported Ag NPs not only avoided the use of chemical reductants but also improved the electrocatalytic activity and stability of Ag NPs. (C) 2014 Elsevier B.V. All rights reserved.