Rechargeable Zn‐H2O hydrolysis battery for hydrogen storage and production

Reactive metals hydrolysis offers significant advantages for hydrogen storage and production. However, the regeneration of common reactive metals (e.g., Mg, Al, etc.) is energy‐intensive and produces unwanted byproducts such as CO2 and Cl2. Herein, we employ Zn as a reactive mediator that can be eas...

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Published in:Angewandte Chemie International Edition 2024-06, Vol.63 (26), p.e202404025-n/a
Main Authors: Cai, Muya, Shi, Hao, Zhang, Yu, Qu, Jiakang, Wang, Hongya, Guo, Yanyang, Du, Kaifa, Li, Wei, Deng, Bowen, Wang, Dihua, Yin, Huayi
Format: Article
Language:English
Subjects:
Aluminum
Carbon dioxide
decoupled water splitting
Desorption
Electrolysis
Energy efficiency
Hydrogen storage
Hydrolysis
hydrolysis reaction
Magnesium
Metals
Renewable energy
Water splitting
Zinc
Zinc oxide
Zn-H2O battery
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Summary:Reactive metals hydrolysis offers significant advantages for hydrogen storage and production. However, the regeneration of common reactive metals (e.g., Mg, Al, etc.) is energy‐intensive and produces unwanted byproducts such as CO2 and Cl2. Herein, we employ Zn as a reactive mediator that can be easily regenerated by electrolysis of ZnO in an alkaline solution with a Faradaic efficiency of >99.9 %. H2 is produced in the same electrolyte by constructing a Zn‐H2O hydrolysis battery consisting of a Zn anode and a Raney‐Ni cathode to unlock the Zn‐H2O reaction. The entire two‐step water splitting reaction with a net energy efficiency of 70.4 % at 80 °C and 50 mA cm−2. Additionally, the Zn‐H2O system can be charged using renewable energy to produce H2 on demand and runs for 600 cycles only sacrificing 3.76 % energy efficiency. DFT calculations reveal that the desorption of H* on Raney‐Ni (−0.30 eV) is closer to zero compared with that on Zn (−0.87 eV), indicating a faster desorption of H* at low overpotential. Further, a 24 Ah electrolyzer is demonstrated to produce H2 with a net energy efficiency of 65.5 %, which holds promise for its real application. A closed‐loop process for H2 storage and production using Zn as an electron carrier to combine a Zn‐H2O hydrolysis battery to generate H2 and an alkaline electrolyzer to regenerate Zn. The Zn‐H2O system can be charged using cheap renewable energy and produce H2 on demand more than 600 times.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.202404025