Redox-mediated decoupled seawater direct splitting for H2 production
Tao Liu, Cheng Lan, Min Tang, Mengxin Li, Yi-Tao Xu, Huimin Yang, Qingyue Deng, Wenchuan Jiang, Zhiyu Zhao, Yifan Wu, Heping Xie
Abstract
Abstract Seawater direct electrolysis (SDE) using renewable energy provides a sustainable pathway to harness abundant oceanic hydrogen resources. However, the side-reaction of the chlorine electro-oxidation reaction (ClOR) severely decreased direct electrolysis efficiency of seawater and gradually corrodes the anode. In this study, a redox-mediated strategy is introduced to suppress the ClOR, and a decoupled seawater direct electrolysis (DSDE) system incorporating a separate O 2 evolution reactor is established. Ferricyanide/ferrocyanide ([Fe(CN) 6 ] 3−/4− ) serves as an electron-mediator between the cell and the reactor, thereby enabling a more dynamically favorable half-reaction to supplant the traditional oxygen evolution reaction (OER). This alteration involves a straightforward, single-electron-transfer anodic reaction without gas precipitation and effectively eliminates the generation of chlorine-containing byproducts. By operating at low voltages (~1.37 V at 10 mA cm −2 and ~1.57 V at 100 mA cm −2 ) and maintaining stability even in a Cl − -saturated seawater electrolyte, this system has the potential of undergoing decoupled seawater electrolysis with zero chlorine emissions. Further improvements in the high-performance redox-mediators and catalysts can provide enhanced cost-effectiveness and sustainability of the DSDE system.