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

• Published in: Advanced materials (Weinheim) 2022-12, Vol.34 (51), p.e2207747-n/a
• Main Authors: Feng, Yangyang, Shi, Qingmei, Lin, Jing, Chai, Erchong, Zhang, Xiang, Liu, Zhenli, Jiao, Lei, Wang, Yaobing
• Format: Article
• Language: English
• Subjects: bifunctional electrocatalysts; Cathodes; decoupled electrochemical hydrazine splitting; Discharge; Electrocatalysts; Fossil fuels; Hydrazines; Hydrogen; Hydrogen evolution; Hydrogen production; Hydrogen-based energy; Metal foils; Oxidation; Rechargeable batteries; separate hydrogen generation; Splitting; Zn–hydrazine batteries
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202207747

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: 2H2O + 2e− → H2 + 2OH−) and hydrazine oxidation (charge: 1/2 N2H4+2OH−→1/2 N2+2H2O+2e−$1{\rm{/}}2\,{{\rm{N}}_2}{{\rm{H}}_4}{\bm{ + }}2{\rm{O}}{{\rm{H}}^{\bm{ - }}}{\bm{ \to }}1{\rm{/}}2\,{{\rm{N}}_2}{\bm{ + }}2{{\rm{H}}_2}{\rm{O}}{\bm{ + }}2{e^{\bm{ - }}}$). 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 Mo2C/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. A new type of rechargeable Zn–hydrazine battery is proposed for separate and efficient hydrogen generation by temporally decoupled hydrazine splitting. The battery, realized by a bifunctional electrocatalyst, decouples the electrocatalytic hydrogen evolution (2H2O + 2e− → H2 + 2OH−) and hydrazine oxidation (1/2 N2H4+2OH−→1/2 N2+2H2O+2e−)\[(1{\rm{/}}2\,{{\rm{N}}_2}{{\rm{H}}_4} + 2{\rm{O}}{{\rm{H}}^ - } \to 1{\rm{/}}2\,{{\rm{N}}_2} + 2{{\rm{H}}_2}{\rm{O}} + 2{e^ - })\], which achieves separate hydrogen generation, ansimultaneously efficient hydrogen production with low energy input of less than 0.4 V and ultrahigh energy efficiency of 96%.