A fluorine-doped cobalt catalyst sustained a laboratory seawater-electrolysis experiment for 2,450 hours. The peer-reviewed study links its durability to changes in chloride movement near the electrode and oxygen-forming reactions within the catalyst. The cell used natural seawater supplemented with sodium hydroxide; a separate changing-current experiment used simulated seawater.
A small membrane cell continued seawater electrolysis for 2,450 hours with a fluorine-doped cobalt catalyst. The peer-reviewed experiment used a 4 cm² active area at 60 °C, with natural seawater supplemented by 1 M sodium hydroxide. At a current density of 0.5 amperes per square centimetre, voltage degradation was reported as 24.9 microvolts per hour. The comparison iridium oxide catalyst ran for 648 hours.[1]
Chloride reaching the anode can sustain unwanted chlorine reactions and damage the catalyst. During operation, the original cobalt hydroxide became cobalt oxyhydroxide. Researchers propose that fluorine released into the liquid changes the surrounding water structure and encourages close sodium–chloride pairs, restricting chloride movement toward the surface. Raman measurements found chlorine-intermediate signals on comparison catalysts but not on the fluorinated surface.[1]
Fluorine remaining inside the solid shortened the distance between neighbouring cobalt atoms. Oxygen-isotope tracing and infrared measurements examined the associated oxygen-forming pathway. The atomistic calculations used to investigate ion movement did not reproduce the full dynamic solvent environment or the complexity of an actual surface.[1]
The fluctuating-current test used simulated seawater containing sodium hydroxide and sodium chloride. The 1,250-hour experiment alternated among three current densities: 1, 0.5 and 0.25 amperes per square centimetre. These conditions differed from the long natural-seawater run. Cell measurements were reported without subtracting solution resistance; the results concern the laboratory device and the specified electrolyte.[1]
