Binary transitional metal/metal oxide-based catalysts have been proven to be more effective for catalysing water splitting reactions than their single metal oxide counterparts. Here we have successfully designed and synthesised a binary metal oxide composite consisting of CoO and Fe3O4 phases with special CoO (111)/Fe3O4 (311) interface as bifunctional catalysts for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The Co-Fe binary oxide composite showed the overpotential values of eta = 220 mV at -10 mA cm(-2) and eta = 290 mV at -100 mA cm(-2) for HER, and as for the OER performance the catalyst is more efficient than the benchmark catalyst Ir/C requiring the smaller overpotential of eta = 369 mV and 406 mV to deliver a current density of 20 mA cm(-2) and at 100 mA cm(-2), respectively. As a bifunctional catalyst for overall water splitting, the cell can achieve a current density of 10 and 50 mA cm(-2) at cell potentials of 1.92 V and 2.05 V, respectively. In addition, the bifunctional electrode also shows long-term water electrolysis stability at a current density of 50 mA cm(-2) for 24 h.