The metallic cobalt nanoparticles in the bulk solution were obtained by antracene mediated reduction of [CoCl4](2) in the potentiostatic electrolysis in an undivided cell at the potential of the anthracene reduction to radical anion at room temperature in DMF/0.1MBu(4)NCl media. [CoCl4](2) ions are generated by the sacrificial cobalt anode dissolution during the electrolysis. The metal particles are oxidized upon contact with the air to form the oxidized cobalt nanoparticles with a low dispersity (20-30 nm). (C) 2015 Elsevier Ltd. All rights reserved.