Hydrogen gas (H2) as a fuel has the advantages of high energy density (122 kJ g-1) and zero carbon emissions. To meet the growing demand for H2 in the future, green, efficient, and convenient production technologies must be developed. The Al-H2O reaction, which produces H2 by reacting aluminum (Al) with water (H2O), is considered a rapid method for producing H2. However, Al-H2O creates a protective oxide layer on the surface of Al, preventing the production of H2. In this study, we developed a simple method for forming Al-GaInSn alloy by brushing GaInSn-Al2O3 grease onto an Al plate to form an Al/GaInSn-Al2O3/Al sandwich structure. Al2O3 in the sample supports GaInSn, prevents the leakage of GaInSn, and promotes its penetration into the Al lattice to form Al-GaInSn alloy. By forming a liquid phase within the alloy, GaInSn increases the accessibility of Al to the reaction. As a result, the Al-GaInSn alloy can rapidly react with pure H2O to produce H2 at room temperature conditions, with yields as high as ∼93.2%. It was interesting to find that dye-polluted water (methyl orange) could be synchronically purified by the Al-H2O reaction at the same time.