An Unconventional Seawater Acceleration Effect Enables High-Spin Cobalt Sites for Industrial-Level Seawater Electrooxidation

Catalytic seawater electrolysis is a valuable renewable energy generation process. However, it is restricted by the intricate and corrosive ionic nature of seawater which hinders oxygen evolution reaction (OER), one of the reactions governing seawater electrolysis. Herein, we introduce an effective approach that not only withstands, but also harnesses the potential of complex ions in seawater to enhance the efficiency and durability of OER. Unlike conventional strategies that address adverse effects through catalyst surface modification, we found that seawater actively facilitates the reconstruction of catalysts with high-spin sites. In situ characterizations suggest that the selective adsorption of Cl⁻ from seawater on high-spin Co sites in alkaline seawater accelerates catalyst reconstruction, contributing to the rapid formation of high-valence Co, which enhances OER activity. The resulting reconstructed wrinkled nanosheets also create additional active Co sites and accelerate electrolyte transport. As a result, we achieve an overpotential as low as 377 mV at a current density of 1 A cm⁻², showcasing nearly 100% oxygen evolution efficiency in alkaline seawater. Notably, our approach achieves a remarkable current density of 2.13 A cm⁻² prior to the onset of the chlorine evolution reaction, underscoring its potential for efficient and sustainable seawater electrocatalysis.