Recent Advances in Bipolar Membrane Engineering for Direct Seawater Electrolysis: Improved Efficiency and Stability for Hydrogen Generation

Direct seawater electrolysis (DSE) offers a sustainable pathway for large-scale hydrogen production by exploiting Earth's most abundant water resource. Yet, its practical implementation is hindered by chloride-induced anodic corrosion, the competing chlorine evolution reaction (ClER), and severe inorganic scaling at industrial current densities. Bipolar membranes (BPMs) have recently emerged as a promising solution, enabling asymmetric pH environments through internal water dissociation at the junction. This configuration accelerates hydrogen evolution under alkaline conditions and oxygen evolution under acidic/near-neutral media, while effectively suppressing Cl^- crossover and cathodic precipitation. Unlike conventional reviews, this work provides a focused analysis of BPM-based strategies for DSE, emphasizing interfacial engineering, catalytic junction design, and long-term membrane durability under saline operation. We further highlight the synergistic integration of BPMs with selective electrocatalysts and chloride-blocking overlayers, which has delivered significant gains in Faradaic efficiency, corrosion resistance, and operational stability. Finally, we delineate the pivotal challenges that must be surmounted to advance this technology toward practical realization, namely, the scalable fabrication of robust BPM architectures, the acceleration of interfacial water dissociation kinetics, and the precise regulation of selective ion transport to ultimately enable efficient and chlorine-free hydrogen generation directly from seawater.