Advances in direct seawater electrolysis for green hydrogen production: emerging technologies and future perspectives

Given the potential exacerbation of global freshwater scarcity due to current hydrogen production via water electrolysis using freshwater, the abundance of seawater offers a promising avenue for sustainable green energy production and storage powered by renewable energy through direct seawater electrolysis (DSE). However, the complex composition of seawater presents higher demands for the design of catalysts and electrolyzers. Although a large number of works have focused on the catalysts and electrolyzers of DSE in recent years, very few reviews offer a holistic perspective that integrates both electrolyzers and catalysts. In this review, we first quantify the freshwater resource and cost pressures associated with green hydrogen production from freshwater electrolysis and demonstrate the technical and economic feasibility of DSE. After discussing the principles and challenges of DSE, we continue with a comprehensive review of the latest research trends and advances in catalysts and electrolyzers, highlighting the existing issues and technological bottlenecks. We found that most of the catalysts developed for DSE so far struggle to balance the required activity, selectivity, and stability for efficient operation. Existing electrolyzers for DSE face an urgent need to address the impact of impurity ions on the membrane and electrodes. Finally, based on current progress, we provide insights and perspectives on the future development and application of DSE hydrogen production technology. This review explores the value of DSE using renewable energy and provides a comprehensive review of seawater electrolysis for hydrogen production from the perspectives of catalysts and electrolyzers. It fills the gap in the current in-depth and systematic discussion of catalysts and electrolyzers in DSE technology, offering research directions for scholars and promoting future development in this field.