Decoupled Electrochemical Hydrazine "Splitting" via a Rechargeable Zn-Hydrazine Battery.
basic_science · Level V
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- Record sourced from PubMed, PMID 36189857.
- Also identified by DOI 10.1002/adma.202207747.
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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<sub>2</sub> O + 2e<sup>-</sup> → H<sub>2</sub> + 2OH<sup>-</sup> ) and hydrazine oxidation (charge: <math xmlns="http://www.w3.org/1998/Math/MathML"> <semantics><mrow><mn>1</mn> <mi>/</mi> <mn>2</mn> <mtext> </mtext> <msub><mi>N</mi> <mn>2</mn></msub> <msub><mi>H</mi> <mn>4</mn></msub> <mo>+</mo> <mn>2</mn> <msup><mtext>OH</mtext> <mo>-</mo></msup> <mo>→</mo> <mn>1</mn> <mi>/</mi> <mn>2</mn> <mtext> </mtext> <msub><mi>N</mi> <mn>2</mn></msub> <mo>+</mo> <mn>2</mn> <msub><mi>H</mi> <mn>2</mn></msub> <mi>O</mi> <mo>+</mo> <mn>2</mn> <msup><mi>e</mi> <mo>-</mo></msup> </mrow> <annotation>$1{\rm{/}}2\,{{\rm{N}}_2}{{\rm{H}}_4}{\bm{ + }}2{\rm{O}}{{\rm{H}}^{\bm{ - }}}{\bm{ \to }}1{\rm{/}}2\,{{\rm{N}}_2}{\bm{ + }}2{{\rm{H}}_2}{\rm{O}}{\bm{ + }}2{e^{\bm{ - }}}$</annotation></semantics> </math> ). 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<sub>2</sub> 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<sup>-1</sup> ) 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.