Seawater Electrolysis for Hydrogen Production: Objectives and Pathways
The global transition to low-carbon economies necessitates scalable hydrogen production via water electrolysis powered by renewable energy. Industry forecasts project global hydrogen demand to exceed 469 million tons per year by 2050, with clean hydrogen comprising 93% of the total. Meeting an annual clean hydrogen demand of 436 Mt would require daily water consumption of 15 Mt, yet major wind and solar installations are concentrated in arid and semi-arid regions with limited freshwater resources. China exemplifies this mismatch: Xinjiang added 42.11 GW of renewable capacity in 2024, far exceeding Fujian's 7.93 GW, while possessing only 80 billion cubic meters of freshwater compared to Fujian's 130 billion. This geographical constraint renders freshwater-dependent electrolysis technologies—alkaline water electrolyzers (AWE), proton exchange membrane electrolyzers (PEMWE), and anion exchange membrane electrolyzers (AEMWE)—increasingly untenable for large-scale deployment. Seawater electrolysis, either indirect (desalination followed by electrolysis) or direct (corrosion-resistant electrodes in untreated seawater), offers a viable pathway. However, inherent impurities including Ca2+, Mg2+, and Cl− impose severe cathodic and anodic challenges. Recent advances in corrosion-resistant, highly active, and selective electrodes now meet industrial requirements for alkaline seawater electrolysis. Electrodes with anti-fluctuation capabilities and electrolyte engineering strategies enable stable operation with intermittent renewable power. Lower water quality requirements simplify system architecture and reduce land footprint, while Cl− tolerance permits treatment of complex water sources. These developments position seawater electrolysis as a critical component of future zero-carbon energy systems.