The development of bifunctional catalysts enables the simultaneous operation of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in the same electrolyte. It is feasible to design high-performance catalysts by the addition of impurity atoms and the construction of composition. Herein, Fe-Ni₃P/Fe-CoP₃ nanostructures are obtained using metal–organic framework (MOF) as the precursor. It shows an overpotential of 71.7 mV (10 mA/cm²) for HER and 263.3 mV (50 mA/cm²) for OER under alkaline condition. Moreover, it also presents an OER overpotential of only 325.3 mV at the current densities of 1.5 A/cm². Using the catalyst as electrodes, the water electrolysis device provides a voltage of 1.566 V at 50 mA/cm². Density functional theory calculations reveal that the introduction of iron atoms and the presence of heterogeneous structures optimize the hydrogen adsorption energy.