Grain boundary phase control via synergistic Sb doping and In regulation for enhanced hydrogen production in aluminum alloys

Abstract

Activating Al-based alloys with low-melting-point metals is an effective strategy to enhance their hydrogen production performance via hydrolysis. Compared to alloys dominated by the In₃Sn phase, Al-Ga-In-Sn quaternary alloys designed to predominantly form the InSn₄ grain boundary (GB) phase offer higher economic efficiency due to their lower indium mass fraction, though they typically exhibit insufficient hydrogen production performance. In this work, a series of Al-Ga-In-Sn-Sb alloys were prepared via high-temperature melting by introducing Sb doping and In regulation. By regulating GB phases’ quantity and morphology, the hydrogen production performance was significantly improved. At 1.10 wt% Sb, the alloy achieved hydrogen yields of 94.38% at 30 °C and 97.4% at 40 °C, with average rates of 67.514 and 163.055 mL/(min·g Alloy), respectively. Remarkably, as the temperature increased to 50 °C, the generation rate surged to 345.727 mL/(min·g Alloy) with a full 100% yield. Comprehensive characterizations and analysis revealed that the enhanced reactivity results from in-situ formed AlSb-promoted heterogeneous nucleation of InSn₄ and the optimized GB phases’ morphology induced by elemental In. Conversely, excessive Sb doping triggers AlSb agglomeration and the morphological reversion of GB phases, thereby suppressing the hydrolysis kinetics. Ultimately, this work provides a compositional design strategy for developing highly efficient and cost-effective hydrogen-producing alloys for practical applications.