Recent advancements in heterostructure-based electrocatalysts for sustainable hydrogen production through seawater splitting

) gas as a promising clean energy carrier. However, global freshwater shortages hinder traditional water electrolysis. Seawater electrolysis has emerged as a viable alternative, leveraging the abundance and high ionic conductivity of saltwater. Yet, the complex composition of seawater, rich in chloride ions and other impurities, poses significant challenges, including competing chlorine evolution reactions (CERs), electrode corrosion, and stability concerns. This comprehensive review offers unique insight into seawater splitting mechanisms, with a focus on the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the CER under acidic, neutral, and alkaline conditions. We also discuss emerging mechanisms, such as lattice oxygen-mediated (LOM) and dual-metal-site mechanism (DMSM) routes, which show potential for improving OER kinetics and stability. This review emphasizes recent advances in heterostructure-based electrocatalysts, particularly those derived from transition metal oxides, hydroxides, phosphides, chalcogenides, nitrides, and carbon composites. These electrocatalysts demonstrate enhanced activity, selectivity, and durability under realistic seawater conditions. This study aims to guide the rational design of next-generation electrocatalysts, addressing current challenges and opportunities for the scalable and sustainable production of green hydrogen from abundant seawater.