Seawater Treatment Technologies for Hydrogen Production by Electrolysis—A Review

Green hydrogen, produced by water electrolysis using renewable energy sources (RES), is an emerging technology that aligns with sustainable development goals and efforts to address climate change. In addition to energy, electrolyzers require ultrapure water to operate. Although seawater is abundant on the Earth, it must be desalinated and further purified to meet the electrolyzer’s feeding water quality requirements. This paper reviews seawater purification processes for electrolysis. Three mature and commercially available desalination technologies (reverse osmosis, multiple-effect distillation, and multi-stage flash) were examined in terms of working principles, performance parameters, produced water quality, footprint, and capital and operating expenditures. Additionally, pretreatment and post-treatment techniques were explored, and the brine management methods were investigated. The findings of this study can help guide the selection and design of water treatment systems for electrolysis.