Effect of low concentration hydroxides on Al hydrolysis for hydrogen production

Using hydroxides as promoters to accelerate Al hydrolysis is a widely researched hydrogen production technology, and its hydrogen production performance closely depends on hydroxide type and concentration. In this study, the impacts of different hydroxides with low concentration on Al hydrolysis dynamics are compared. The results indicate that different hydroxides play obvious different roles in Al hydrolysis. NaOH, KOH, Ca(OH)2, Mg(OH)2, Fe(OH)3 and Al(OH)3 promote Al hydrolysis dynamics, while Cu(OH)2 has an inhibiting effect on Al hydrolysis. Mechanism analyses reveal that the promoting effect of NaOH, KOH and Mg(OH)2 is mainly ascribed to OH−, while the catalytic effect of Al(OH)3 and Fe(OH)3 is the key reason for their promoting effect. For Ca(OH)2, both OH− and the reaction between Ca(OH)2 and Al(OH)4- results in its excellent promoting effect. The present research indicates that Ca(OH)2 is a more effective promoter than NaOH and KOH to enhance hydrogen production performance of Al hydrolysis.