Application of a bifunctional electrocatalyst for simultaneously producing H-2 and O-2 is still a great challenge, which is important for the enhancement of the overall efficiency of water electrolysis. Taking advantages of the superior conductivity of N-doped graphite carbon, the good electrocatalytic performance of Co-based alloys for HER and excellent performance of cobalt-based oxide for OER, herein, we prepare a CoFex-CoFe2O4/N-doped carbon nanocomposite with a hierarchical porous structure used to HER and OER by pyrolysis of a new single source precursor {[Co(H2O)(6)][Fe(Hedta)Cl](2)center dot 4H(2)O]}. CoFex-CoFe2O4/N-doped carbon displays high activity with small overpotentials of respective 159 and 257mV required to achieve a current density of 20 mA cm(-2) as well as catalytic durability for HER and OER in 1.0 M KOH. Furthermore, this bifunctional electrocatalyst enables an alkaline electrolyzer with 20 mA cm(-2) at a cell voltage of similar to 1.68 V. The good performance of CF-CFO/NC for HER and OER can be attributed to the low charge transfer impedance, a porous structure and the synergistic role of cobalt-based alloy and cobalt-based mixed metal oxide. This work may provide a new approach to prepare an efficient, cost-effective and superior electrocatalyst in large scale using earth-abundant elements. (C) 2018 Elsevier Ltd. All rights reserved.