Yingshuang Xu ^{a, 1}, Honghao Lv ^{a, 1}, Huasen Lu ^a, Qinghao Quan ^a, Wenzhen Li ^b, Xuejing Cui ^a,

Guangbo Liu ^a, *, and Luhua Jiang ^a, *

^a Nanomaterial & Electrocatalysis Laboratory, College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, P. R. China

^b Department of Chemical & Biological Engineering, Iowa State University, Ames, IA 50011-1098, Unites States.

^*Email: liugb@qust.edu.cn; luhuajiang@qust.edu.cn

¹These authors contributed equally to this work.

ABSTRACT:

Direct seawater electrolysis to sustainable production of hydrogen fuel is attractive, given the abundant seawater resource on Earth. Nevertheless, current seawater electrolysis systems necessarily require external power grid to drive the electrolysis process, which are neither able to achieve continuous hydrogen production nor applicable to mobile and undersea apparatuses. Herein, we demonstrate a self-powered, direct seawater electrolysis system driven by Mg/seawater batteries for continuous hydrogen production. For a case study, a heterostructured MoNi/NiMoO₄ is prepared to catalyze the hydrogen evolution reaction (HER) at the cathodes of both the Mg/seawater battery and the seawater electrolysis, displaying a superior performance surpassing a commercial Pt/C with the overpotential as low as 256 mV at 10 mA cm^-2 in seawater. The Mg/seawater battery achieves a peak power density of 21.08 mW cm^-2, serving as a power source to drive seawater electrolysis. The self-powered system yields a total hydrogen evolution rate of 12.11 mL cm^-2 h^-1 and conversion efficiency of Mg-to-hydrogen up to 83.97%. Such a self-powered direct seawater electrolysis system provides an intriguing strategy for the continuous acquisition of hydrogen fuel from infinite seawater without any external power grids.

KEYWORDS: Mg/seawater battery; self-powered electrolysis; hydrogen production; seawater electrolysis system.