We demonstrate an extremely facile in-situ pyrolysis followed by the reduction of partial Co2+ route to synthesize novel Ketjen black carbon (KB) supported CoO@Co-N-C (denoted as CoO@Co-NC/KB) nanochains using KB, urea and cobalt (II) acetate as co-precursors. The as-prepared CoO@Co-NC/KB displays higher electrocatalytic activity, smaller Tafel slope and better durability for the oxygen evolution reaction than those of the benchmark commercial RuO2 catalyst in 1.0 M KOH solution, far outperforming the control groups (i.e. CoO@Co-g-C3N4/KB, Co-NC/KB, CoO-NC/KB, CoO@Co/KB, CoO@Co-NC and Co3O4-NC/KB). The remarkable electrocatalytic performance of CoO@Co-NC/KB is primarily credited to the synergistic effect between Co and CoO species with a core-shell structure, increased active sites and considerably enhanced electronic conductivity. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.