Study on the kinetic regulation of hydrogen production from active aluminum composites by ammonium salts

Active aluminum composites are ideal choices for portable hydrogen sources and are playing an increasingly important role in the field of emergency response. The hydrogen production rate from their reaction with water is a key factor determining the practical application effectiveness of these materials. This study thoroughly investigates the catalytic effects of four ammonium salts on the hydrogen production rate of active aluminum composites in water reactions. By incorporating four types of ammonium salts (Al/Bi/NH 4 Cl, Al/Bi/(NH 4 ) 2 C 2 O 4 , Al/Bi/(NH 4 ) 2 CO 3 , and Al/Bi/NH 4 H 2 PO 4 ) along with bismuth into aluminum powder and preparing them through ball milling, four types of active aluminum composites were obtained. A detailed analysis was conducted on the microstructures of these composites and their hydrogen production performance in water reactions. The results show that NH 4 Cl can form a multilayer structure on the surface of Al/Bi/NH 4 Cl, allowing this composite to exhibit the best hydrogen production performance, reaching a maximum hydrogen production rate of 14.4 mL g −1  s −1 and a maximum hydrogen volume of 948 mL g −1 at 45 °C. Additionally, the mechanisms by which different ammonium salts influence the hydrogen production rate of active aluminum composites in water reactions were discussed in detail. The unique multilayer structure of Al/Bi/NH 4 Cl and the excellent solubility of NH 4 Cl contribute to accelerating particle rupture and enhancing the reaction rate. More importantly, H + ions released from the hydrolysis of NH 4 Cl can neutralize OH − produced during the reaction, effectively controlling the pH value of the reaction medium, preventing the deposition of aluminum hydroxide on the aluminum surface, and thus maintaining a larger reaction surface area and continuous reaction activity. The study shows that adjusting the types of ammonium salts can effectively regulate the water reaction kinetics of active aluminum composites.