A novel composite ultrafine cobalt nanoparticles-reduced graphene oxide (Co-RGO) was firstly synthesized through a modified one-step solvothermal method with Co(OH)(2) as the precursor. The prepared low-cost Co-RGO composite exhibited excellent catalytic activity for the reduction of highly toxic Cr(VI) to nontoxic Cr(III) at room temperature when formic acid (HCOOH) was employed as the reductant, and its catalytic performance was even comparable with that of noble metal-based catalysts in the same reduction reaction. Moreover, Co-RGO composite could be readily recovered under an external magnetic field and efficiently participated in recycled reaction for Cr(Vl) reduction. (C) 2017 Elsevier B.V. All rights reserved.