Decoupled Electrochemical Hydrazine “Splitting” via a Rechargeable Zn–Hydrazine Battery

Abstract Hydrogen generation via electrochemical splitting plays an important role to achieve hydrogen economy. However, the large‐scale application is highly limited by high cost and low efficiency. Herein, a new type of rechargeable Zn–hydrazine (Zn–Hz) battery is proposed and realized by a bifunctional electrocatalyst based on two separate cathodic reactions of hydrogen evolution (discharge: 2H 2 O + 2 e − → H 2 + 2OH − ) and hydrazine oxidation (charge: ). This Zn–Hz battery, driven by temporally decoupled electrochemical hydrazine splitting on the cathode during discharge and charge processes, can generate separated hydrogen without purification. When the highly active bifunctional cathode of 3D Mo 2 C/Ni@C/CS is paired with Zn foil, the Zn–Hz battery can achieve efficient hydrogen generation with a low energy input of less than 0.4 V (77.2 kJ mol −1 ) and high energy efficiency of 96%. Remarkably, this battery exhibits outstanding long‐term stability for 600 cycles (200 h), achieving continuous hydrogen production on demand, which presents great potential for practical application.