Decoupled electrolysis for hydrogen production and hydrazine oxidation via high-capacity and stable pre-protonated vanadium hexacyanoferrate.

Lv, Fei; Wu, Jiazhe; Liu, Xuan; Zheng, Zhihao; Pan, Lixia; Zheng, Xuewen; Guo, Liejin; Chen, Yubin · Nat Commun · 2024

basic_science · Level V

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Abstract

Decoupled electrolysis for hydrogen production with the aid of a redox mediator enables two half-reactions operating at different rates, time, and spaces, which offers great flexibility in operation. Herein, a pre-protonated vanadium hexacyanoferrate (p-VHCF) redox mediator is synthesized. It offers a high reversible specific capacity up to 128 mAh g<sup>-1</sup> and long cycling performance of 6000 cycles with capacity retention about 100% at a current density of 10 A g<sup>-1</sup> due to the enhanced hydrogen bonding network. By using this mediator, a membrane-free water electrolytic cell is built to achieve decoupled hydrogen and oxygen production. More importantly, a decoupled electrolysis system for hydrogen production and hydrazine oxidation is constructed, which realizes not only separate hydrogen generation but electricity generation through the p-VHCF-N<sub>2</sub>H<sub>4</sub> liquid battery. Therefore, this work enables the flexible energy conversion and storage with hydrogen production driven by solar cell at day-time and electricity output at night-time.