Liquid metal-induced aluminum activation by thermal sintering for hydrogen production through water splitting reaction

This study investigates aluminum activation by thermal sintering using liquid metals (gallium, eutectic Ga–Sn alloy, and eutectic Ga-Sn-In alloy) as activating agents for hydrogen production via water splitting reaction. Activated aluminum composites are synthesized by spraying aluminum foils with liquid metal particles then thermally sintering them. Activated composites react spontaneously with water at ambient conditions to produce hydrogen. Composites of aluminum with gallium react very slowly (10–20 h) with water at high temperature (∼70 °C.). Notably, the reaction of aluminum composites with eutectic alloys of Ga with Sn and Sn–In is extremely fast (3–18 min) in comparison to those with Ga metal. Experiments showed that a very small ratio of Ga-Sn-In (∼7 mass %) promotes aluminum reaction with water achieving ∼70 % hydrogen yield. The amount of gas produced from the reaction and hydrogen yield are found to depend on the type of liquid metal and the ratio of liquid metal to aluminum. The reaction rate is highly dependent on reaction temperature, for instance increasing the reaction temperature from 10 °C to 30 °C leads to reducing the reaction time from 65 min to 10 min. The activated composites have a very long shelf life and retain more than 70 % of their activity after storage for three months in ambient conditions. The role of liquid metal components in activating aluminum is analyzed and a mechanism of reaction is proposed.