A sodium-ion-conducted asymmetric electrolyzer to lower the operation voltage for direct seawater electrolysis

• Published in: Nature communications Vol. 14; no. 1; p. 3934
• Main Authors: Shi, Hao, Wang, Tanyuan, Liu, Jianyun, Chen, Weiwei, Li, Shenzhou, Liang, Jiashun, Liu, Shuxia, Liu, Xuan, Cai, Zhao, Wang, Chao, Su, Dong, Huang, Yunhui, Elbaz, Lior, Li, Qing
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04-07-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 147/137; 639/301/299/886; 639/638/161/886; 639/638/224/909/4086; Asymmetry; Calcium ions; Catalysts; Chemical analysis; Corrosion; Density functional theory; Electricity; Electrolysis; Electrolytes; Energy consumption; Humanities and Social Sciences; Hydrogen; Hydrogen evolution; Iron; Low voltage; Magnesium; multidisciplinary; Nanotechnology; Nanowires; Precipitates; Raman spectroscopy; Science; Science (multidisciplinary); Seawater; Side reactions; Sodium; Sodium channels (voltage-gated); Water analysis; United States > US
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-39681-1

Hydrogen produced from neutral seawater electrolysis faces many challenges including high energy consumption, the corrosion/side reactions caused by Cl
-
, and the blockage of active sites by Ca
2+
/Mg
2+
precipitates. Herein, we design a pH-asymmetric electrolyzer with a Na
+
exchange membrane for direct seawater electrolysis, which can simultaneously prevent Cl
-
corrosion and Ca
2+
/Mg
2+
precipitation and harvest the chemical potentials between the different electrolytes to reduce the required voltage. In-situ Raman spectroscopy and density functional theory calculations reveal that water dissociation can be promoted with a catalyst based on atomically dispersed Pt anchored to Ni-Fe-P nanowires with a reduced energy barrier (by 0.26 eV), thus accelerating the hydrogen evolution kinetics in seawater. Consequently, the asymmetric electrolyzer exhibits current densities of 10 mA cm
−2
and 100 mA cm
−2
at voltages of 1.31 V and 1.46 V, respectively. It can also reach 400 mA cm
−2
at a low voltage of 1.66 V at 80 °C, corresponding to the electricity cost of US$1.36 per kg of H
2
($0.031/kW h for the electricity bill), lower than the United States Department of Energy 2025 target (US$1.4 per kg of H
2
).
Hydrogen produced directly from neutral seawater is promising but challenging due to seawater’s complex composition. Here, the authors report a Na
+
-conducted pH-asymmetric electrolyzer that can directly split seawater into hydrogen with low electricity cost and nearly zero chloride interference.