Research on rapid hydrogen production from aluminum composites: Regulating the hydrolysis kinetics of aluminum composites through sodium salts

Enhancing the aqueous reactivity of aluminum-based composites under ambient conditions is crucial for their application as portable, on-demand hydrogen sources in outdoor and emergency settings. This study synthesizes three aluminum composites (Al-Bi-Na 2 SO 3 , Al-Bi-Na 3 PO 4 , and Al-Bi-Na 2 CO 3 ) via mechanical ball milling to systematically evaluate the effect of anion type on the hydrolysis kinetics of aluminum. The microstructural features and hydrogen production performance of these composites are thoroughly examined. Results indicate that ball milling facilitates the uniform dispersion of bismuth and sodium salts over the aluminum particle surfaces. The composites exhibit distinctly different hydrolysis behaviors depending on the anion species. Notably, Al-Bi-Na 2 SO 3 shows the highest reactivity, reaching a maximum hydrogen generation rate of 5.35 mL g −1 s −1 and a total yield of 1019 mL g −1 at 40 °C. Impressively, it sustains rapid hydrogen release even at 0 °C. Real-time monitoring of temperature and pH variations during hydrolysis provides further insight into the reaction dynamics. The excellent performance of Al-Bi-Na 2 SO 3 is due to the key role of SO 3 2− , which enables the formation of soluble Al 2 (SO 3 ) 3 with Al 3+ produced during the reaction, thereby effectively mitigating surface passivation. Moreover, the SO 3 2− /H 2 SO 3 system provides mild buffering capacity that promotes an alkaline shift in the reaction environment, further accelerating aluminum hydrolysis. This study underscores the crucial role of anion selection in sodium salts for tuning the hydrolysis kinetics of aluminum composites, providing a strategic pathway for designing high-performance hydrogen generation systems operable under ambient conditions. • Anion-engineered Al-Bi composites achieve low activation energy (12.4 kJ/mol) for hydrolysis. • Al-Bi-Na 2 SO 3 demonstrates maximum hydrogen production volumes of 5.35 mL g −1 s −1 (40 °C). • SO 3 2− uniquely accelerates kinetics via soluble Al 2 (SO 3 ) 3 formation and weak buffering, enabling rapid pH rise. • Mechanistic synergy between ball-milling (oxide disruption) and anion selection enables portable H 2 generation.