Chlorine Evolution Suppression in Seawater Electrolysis: From Mechanistic Insights and Catalyst Design to Device‐Level Innovations

Seawater electrolysis has emerged as a highly promising technology for sustainable hydrogen production, offering the dual advantages of utilizing abundant seawater resources and compatibility with offshore renewable energy systems. However, the practical implementation of this technology faces a critical challenge: the competing chlorine evolution reaction (CER) at the anode. This side reaction not only reduces the Faradaic efficiency for oxygen production but also induces severe catalyst corrosion through chloride-induced degradation pathways, ultimately compromising the durability and economic viability of electrolysis systems. To address these challenges, this review provides a comprehensive overview of recent advances in CER suppression strategies, systematically categorizing them into three interconnected approaches: enhancing catalyst selectivity through the construction of chloride-blocking layers and other selective adsorption strategies; improving intrinsic oxygen evolution reaction activity via electronic structure modulation, interface engineering, and other activation methods; and reinforcing catalyst stability using corrosion-resistant materials and related protective approaches. Furthermore, we examine electrolyte optimization and innovative electrolyzer designs that contribute to system-level CER mitigation. By synthesizing these developments, this review aims to establish fundamental principles and practical guidelines for designing highly efficient and durable seawater electrolysis systems, thereby accelerating the industrial implementation of this sustainable hydrogen production technology.