Characterized on hydrogen properties and mechanism of Al–Sn–Bi composite powder in salt solutions

Abstract

Using low-melting point elements to promote the Al/H2O reaction has garnered considerable attention because it is an economical approach to hydrogen supply. Herein, .Al–Sn–Bi composite powder was prepared through milling. The Al–Sn–Bi composite powder and the hydrolysate were investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the hydrolysis products is primarily AlOOH. The properties of the Al/H2O reaction were systematically characterized in salt solutions. Results show that the presence of Sn and Bi is beneficial to achieve short introduction times and large Al/H2O reaction rates. The hydrogen generation rate of the Al–Sn–Bi composite is 4566 mL min−1 g−1 and 3600 mL min−1·g−1 with NaCl and Na2SO4 solutions, respectively and the hydrogen production efficiency can reach 100% in 1 min. Additionally, the mechanism of Sn and Bi promoting Al/H2O reaction was characterized by density functional theory (DFT) calculations. The DFT calculations show that Sn and Bi replace 1/8 ML, 1/4 ML and 1/2 ML surface atoms of Al (111), the surface chemical potential increases with increasing doping concentration, and the electrode potential decreases with increasing doping concentration. The presence of Sn and Bi increases the surface chemical potential and reduces the electrode potential, this is conducive to the microcell reaction and promotes the Al/H2O reaction.