[en] Highlights: • One-step conversion from NiFePPc to N-doped carbon supported Ni-Fe nanoparticles. • The [email protected] exhibits superior catalytic activity and durability for OER. • The resultant samples also exhibit high activity for HER. • The bi-functional [email protected] shows excellent performance in the symmetrical setup. As the two half-reactions in water splitting, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) are traditionally carried out with high-cost and scarce precious metals (e.g., Ru, Ir and Pt) as the electrocatalysts, which hampers the large-scale applications in water splitting. Herein, we developed a low-cost and efficient method to prepare the nitrogen-doped carbon supported nickel-iron nanoparticle ([email protected]) electrocatalysts, simply by one-step conversion from cross-linked polyphthalocyanine under the direct pyrolysis treatment. The resultant [email protected] electrocatalysts exhibit the efficient catalytic activity and durability for both OER and HER as bi-functional electrodes in water splitting device. The water splitting device based on the same [email protected] electrocatalyst at both sides of anode and cathode can operate with lower cell voltage (1.81 V, at 10 mA cm⁻²) in 1 M KOH aqueous electrolyte, as well as excellent durability (over 15 h of operation at 8, 10 and 20 mA cm⁻²) and high reversibility. The excellent electrocatalytic performance indicates that [email protected] electrocatalysts can be the promising replacement of the precious metals for more practical and cost-efficient water splitting. This work develops a new method for the preparation of high efficient and low-cost Ni-based electrocatalysts for symmetrical water splitting devices.