Direct seawater electrolysis for green hydrogen production: electrode designs, cell configurations, and system integrations

Direct seawater electrolysis (DSE) is a promising technology for sustainable hydrogen production, utilizing abundant marine resources. However, industrialization of DSE faces significant long-term stability challenges due to the complex composition of seawater, which contains various ions and microorganisms that can lead to both chemical and physical degradation of the electrolysis system. For instance, the presence of chloride ions (Cl⁻) hinders the desired oxygen evolution reaction (OER) because competing chlorine evolution reactions (CER) occur and adversely impact electrode materials, resulting in low system efficiency and poor longevity. To enhance long-term stability of DSE, researchers are investigating robust electrocatalysts and advanced surface modifications that improve protection against corrosive environments and enhance selectivity. Innovative electrode designs are also being developed to manage bubble transport and decrease precipitation. Additionally, the design of electrolysis cells, such as bipolar membrane cells, offers a viable solution by minimizing Cl⁻ transport and corrosive environment. With an increasing number of offshore renewable energy projects, the integration of effective DSE technologies in the offshore environment is critical. This review provides the state-of-the-art of electrodes, cells and systems, contributing to the development of DSE for long-term stable operation.