Guangbo Liu¹, Huasen Lu¹, Yingshuang Xu¹, Qinghao Quan¹, Honghao Lv¹, Xuejing Cui¹, Jie Chen¹, Luhua Jiang ^1,*, R. Jürgen Behm^2,*

¹ College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao266042, P. R. China

² Institute of Theoretical Chemistry, Ulm University, Ulm 89069, Germany

ABSTRACT

A seawater-electrolyte Mg/H₂O battery, converting chemical energy of Mg into electricity and hydrogen via anodic/chemical oxidation of Mg and cathodic reduction of water, combines electricity generation and H₂ production, thus is not only ideal power source for marine equipment, but also intriguing on-line/offshore H₂ generator for fuel cells. Nonetheless, it substantially suffers from the slow kinetics of hydrogen evolution reaction at the cathode. Herein, we propose a proof-of-concept design of a photo-assisted Mg/H₂O battery with simulated seawater (0.5 M NaCl, pH = 6.8) as the electrolyte, and a CuSCN/Cu₂O photocathode is applied to promote the hydrogen evolution reaction kinetics and battery performance. Under illumination, the CuSCN/Cu₂O reveals a photocurrent density of up to 4.32 mA cm^-2 at 0 V vs. reversible hydrogen electrode, over 1.7 times higher than that of Cu₂O. A photo-assisted Mg/H₂O battery is demonstrated with a peak power density of 1.18 mW cm^-2 and a H₂ production rate of 0.56 mL cm^-2 min^-1 under illumination, which is 3.6 and 9.6 times higher than those obtained in the dark. This novel strategy of a photo-assisted Mg/H₂O battery enables the simultaneous conversion of photo- and chemical energy into electric energy and hydrogen from seawater.

KEYWORDS: Photo-assisted Mg/H₂O battery; electric energy; hydrogen evolution; CuSCN/Cu₂O; photocathode.

^*Email: luhuajiang@qust.edu.cn, juergen.behm@uni-ulm.de

https://doi.org/10.1016/j.cej.2022.140875