Cell preservation strategies in direct seawater electrolysis based on cost-effective anion exchange membrane technology

A scalable production of low-cost hydrogen from renewable sources should include electrolysis technology fed with seawater as alternative substrate to fresh water. A cost-effective anion exchange membrane-based water electrolysis technology directly fed with seawater was studied. Different water sources including Mediterranean seawater, seawater surrogates and ultra-pure milliQ water were investigated as water feed for the cell in combination with various materials and operating strategies. Suitable cell modifications were studied to protect the system against degradation. A conventional anion exchange membrane electrolysis cell fed with seawater showed poor performance and fast degradation. The performance and stability substantially improved when the seawater was fed only to the cathode through a hydrophobic microporous carbon layer. A promising performance of 1.72 V/cell at 1 A cm-2 was achieved at 50°C after a durability test of about 150 hrs using seawater and KOH fed directly fed to the cathode, with a voltage efficiency of about 86% vs. H2 HHV. The direct seawater feed strategy was theoretically compared to a two-step process involving seawater desalination by reverse osmosis before being fed to the electrolysis device.