Multiscale Engineering of Nonprecious Metal Electrocatalyst for Realizing Ultrastable Seawater Splitting in Weakly Alkaline Solution

Seawater electrolysis is an attractive technique for mass production of high-purity hydrogen considering the abundance of seawater. Nevertheless, due to the complexity of seawater environment, efficient anode catalyst, that should be, cost effective, highly active for oxygen evolution reaction (OER) but negligible for Cl-2/ClO- formation, and robust toward chlorine corrosion, is urgently demanded for large-scale application. Although catalysis typically appears at surface, while the bulk properties and morphology structure also have a significant impact on the performance, thus requiring a systematic optimization. Herein, a multiscale engineering approach toward the development of cost-effective and robust OER electrocatalyst for operation in seawater is reported. Specifically, the engineering of hollow-sphere structure can facilitate the removal of gas product, while atom-level synergy between Co and Fe can promote Co sites transforming to active phase, and in situ transformation of sulfate ions layer protects catalysts from corrosion. As a result, the as-developed hollow-sphere structured CoFeSx electrocatalyst can stably operate at a high current density of 100 mA cm(-2) in the alkaline simulated seawater (pH = 13) for 700 h and in a neutral seawater for 20 h without attenuation. It provides a new strategy for the development of electrocatalysts with a broader application potential.

Automated summary

Seawater electrolysis is a viable technique for large-scale production of high-purity hydrogen. However, the complex seawater environment calls for the development of an efficient anode catalyst that is cost-effective, highly active for oxygen evolution reaction (OER), resistant to chlorine corrosion, and negligible for Cl-2/ClO- formation. This study presents a multiscale engineering approach for the development of a cost-effective and robust hollow-sphere structured CoFeSx electrocatalyst that exhibits excellent stability and activity in seawater electrolysis, offering potential for broader applications.