Fe-doped CoNiP@N-doped carbon nanosheet arrays for hydrazine oxidation assisting energy-saving seawater splitting

• Fe-doped Ni 2 P/CoP encapsulated by carbon layers grown on Ni foam are synthesized. • Fe doping, heterostructure, and N-doped carbon are integrated into catalyst. • Fe-CoNiP@NC shows excellent activity for HzOR and HER in alkaline seawater. • It can save 4.03 kWh to generate 1.0 m 3 of H 2 by HzOR assisted hydrogen production. Hydrazine oxidation assisting seawater splitting is a promising strategy to achieve chlorine-free energy-saving hydrogen production. Herein, Fe-doped Ni 2 P/CoP encapsulated by ultrathin nitrogen-doped carbon layers (Fe-CoNiP@NC) with unique nanosheet structure grown on Ni foam are synthesized, which was used as highly efficient and durable bifunctional catalyst for both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER). For the two-electrode system toward overall hydrazine splitting (OHzS) in alkaline seawater, Fe-CoNiP@NC reveals a low cell voltage of 0.56 V at 1000 mA cm −2 , stable operation for 100 h to keep ∼500 mA cm −2 , and nearly 100% Faraday efficiency. Compared to the N 2 H 4 -free seawater system, the OHzS system can save 4.03 kWh for producing 1.0 m 3 of H 2 , realizing energy-saving H 2 production.