Manipulating Al-Ga-based alloys' hydrolysis performance for hydrogen supply by balancing grain growth and liquid metal embrittlement

Al-Ga-based alloys are promising carriers of renewable energy, which can provide hydrogen by hydrolysis in challenging working environments. Manipulating their performance by different process conditions and comprehending the mechanisms are important for achieving directional design synthesis of alloys and enhancing their practicality. This study presents a novel approach to optimizing the hydrogen production performance of Al-Ga-based alloys by precisely controlling the mold temperature during fabrication. Notably, the alloy cast at a mold temperature of 200 °C exhibited the most favorable hydrogen generation performance, achieving a hydrogen generation rate of 1240.7 mL/min·g with a hydrogen yield of 98.0% at 70 °C. Even under ambient conditions (25 °C), the alloy maintained a considerable hydrogen generation rate of 174.3 mL/min·g and a yield of 83.6%. This offers a new strategy for efficient hydrogen generation. Through the application of scanning electron microscopy (SEM), nanoindentation, and custom-designed penetration simulation experiments, we elucidated the dual impact of mold temperature on grain growth and the liquid metal embrittlement (LME) effect within the aluminum matrix. While increased grain size is generally detrimental to the hydrolysis reaction, the concurrent enhancement of the LME effect at elevated mold temperatures favors hydrogen production. We propose a mechanism that reconciles these opposing influences, demonstrating how mold temperature can be leveraged to fine-tune alloy properties. This work not only optimizes alloy performance but also establishes a foundation for designing alloys with superior hydrolysis reactivity by adjusting mold temperatures, thereby reducing production costs and enhancing the efficiency of hydrogen production.