Rapid hydrogen production from hydrolysis of aluminum composites by modulation of chloride salts

In this study, four chlorinated salts were incorporated as catalysts into aluminum composites through ball milling, resulting in the preparation of four activated aluminum composites (Al/Bi/M x Cl y ). The microstructure of these composites was thoroughly examined using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Thermogravimetric Analysis (TGA). Additionally, the hydrogen production characteristics of Al/Bi/M x Cl y during hydrolysis reactions were investigated. The findings indicate that various chloride salts (M x Cl y ) can be uniformly distributed on the surface of the activated aluminum composites. Among the four composites, Al/Bi/NH 4 Cl demonstrated the highest hydrogen production efficiency and volume at temperatures ranging from 10 to 40 °C. Specifically, at 40 °C, Al/Bi/NH 4 Cl achieved a maximum hydrogen generation rate of 82.2 mL‧g −1 ‧s −1 and a total hydrogen volume of 977 mL‧g −1 . Notably, even at 0 °C, Al/Bi/NH 4 Cl maintained a rapid hydrolysis reaction, with a hydrogen production rate of 19.8 mL‧g −1 ‧s −1 and a total hydrogen volume of 908 mL‧g −1 . To elucidate the hydrolysis reaction mechanism, the intermediate products, corrosion potentials, temperature variations, and pH changes within the reaction system were also analyzed in detail. The results confirmed that different M x Cl y catalysts exhibit distinct catalytic mechanisms for the reactive aluminum composites. Particularly, the addition of NH 4 Cl during the preparation process facilitated the formation of a multilayer structure in Al/Bi/NH 4 Cl, which effectively accelerated particle fragmentation during the hydrolysis. Furthermore, the acidic nature of NH 4 Cl efficiently suppressed the increase in solution pH, thereby reducing the deposition of aluminum hydroxide on the particle surfaces and enhancing the overall hydrolysis reaction of aluminum.