Addressing selectivity challenges in seawater splitting: Catalyst design for oxygen and chlorine evolution reactions

Abstract

Direct seawater splitting is a promising pathway for sustainable hydrogen (H₂) production. However, significant challenges persist, particularly at the anode, where the high concentration of chloride ions induces competitive reactions between the chlorine evolution reaction (CER) and the oxygen evolution reaction (OER). Although chlorine gas (Cl₂) has a higher commercial value than oxygen (O₂), selective oxygen generation is often more advantageous for large-scale hydrogen production. Compared with freshwater splitting, seawater splitting introduces additional complexities, including material degradation caused by chlorine corrosion. Therefore, the development of robust electrocatalysts is essential to enhance long-term system stability and overall efficiency, as well as to enable selective Cl₂ or O₂ production. These challenges make seawater splitting inherently more complex than freshwater splitting. This review provides a comprehensive overview of recent advancements in electrocatalysts for seawater splitting, delving into the fundamental mechanisms governing anode reactions, particularly OER and CER. In addition, we critically examine strategies to control reaction selectivity, focusing on designing electrocatalysts that favor one reaction over the other, considering factors such as catalyst composition and structure. Finally, we outline significant opportunities, challenges, and design approaches to guide future research and technological advancements in seawater splitting.