Hydrogen generation by aluminum corrosion in seawater promoted by suspensions of aluminum hydroxide

Abstract Nowadays, new processes of H 2 generation from water via Al corrosion are mainly limited by Al passivation. Here we report on the systematic assessment of H 2 production by corrosion of Al in seawater suspensions prepared with NaAlO 2 . The reported results are encouraging, since it was observed that seawater suspensions tested can prevent Al passivation during H 2 evolution, reaching 100% yields at ca. 700 cm 3 H 2  min −1 . XRD analysis revealed the formation of solid Al(OH) 3 (bayerite) in initial seawater suspensions. So, model suspensions were prepared using NaAlO 2  + Al(OH) 3 in distilled water, which even improved the results obtained in seawater. Suspended particles of Al(OH) 3 act as nuclei in a mechanism of seeded crystallization, which prevents Al surface passivation. Moreover, a synergistic effect of Al(OH) 3 suspensions in combination with NaAlO 2 solutions was key in promoting Al corrosion. The effect of NaCl in aqueous suspensions was also studied, but it was insignificant compared to this synergistic effect. The composition of suspensions was optimized and a 0.01 M NaAlO 2 solution with 20 g dm −3 Al(OH) 3 was selected as candidate to generate H 2 at pH ca. 12 with high efficiency. Consecutive runs of the selected composition were performed obtaining ca. 90% yields in all of them.