Green hydrogen production by alkaline seawater electrolyzers: a transition from lab-scale research to industrial-scale applications

Abstract

Seawater electrolysis offers an alternative to freshwater-based electrolysis owing to its abundant resources and sustainability, making it a key driver in addressing global water scarcity while advancing the hydrogen economy. However, the commercialization of seawater electrolysis faces several challenges including catalyst degradation, membrane fouling, and competing chloride oxidation, which affect its long-term operational stability. This review provides a comprehensive analysis of the fundamentals, advantages, and challenges associated with seawater electrolysis, along with some information on advanced catalysts, new membrane technologies, and unique system designs. Self-supporting electrode architectures, surface protection strategies, and innovative electrolyzer designs used to enhance the durability and ensure sustained operation under industrially relevant conditions are discussed herein. Additionally, this review highlights emerging approaches including the use of in situ purification systems, forward osmosis membranes, and hybrid seawater electrolyzers, which hold significant potential for reducing the operational costs and improving the overall system efficiency. The following systems have demonstrated high performance: asymmetric Na⁺-exchange electrolyzers showing 1.31 V at 10 mA cm⁻² and 1.46 V at 100 mA cm⁻² with an estimated power consumption of ∼3.96 kWh m⁻³ H₂ (LCOH ≈ US$1.96 kg⁻¹), bifunctional Au-Gd-Co₂B@TiO₂ electrodes achieving 1.68 V at 500 mA cm⁻² with ≥200 h stability, and Mo₃Se₄–NiSe core–shell electrodes affording 1.71 V at 10 mA cm⁻² and stable operation for 50 h. We summarize techno-economic metrics (CapEx/OpEx), highlight the current stability gaps between industrial alkaline water electrolyzers (≥60 000 h) and seawater electrolysis systems (≤3200 h), and propose a roadmap to resolve chloride chemistry, membrane fouling, and scale-up issues. Lastly, it presents guidance for future research and industrialization, identifying key areas where innovation is needed to accelerate the development of commercially viable seawater electrolyzers.