Tailoring the hydrogen production behavior of Al-Zn-Sn alloys through their as-solidified microstructures

An advantageous approach for hydrogen production, without greenhouse gas emissions, consists of the reaction of Al alloys with water in alkaline media. This study investigates the rates involved in hydrogen production using directionally solidified Al-5Zn-XSn and Al-10Zn-XSn (X = 10 and 20) [wt.%] alloys, with a particular focus on microstructure-related effects. The results of hydrogen evolution tests in a 1 M NaOH solution demonstrate that an appropriate combination of solute content and microstructure refinement can lead to a 5.7-fold increase in the hydrogen generation rate. Novel experimental equations based on the Hall-Petch relationship are introduced, linking dendritic arm spacings with hydrogen generation rates. It is observed that an excessive amount of Zn in the interdendritic regions has a negative impact on hydrogen generation kinetics. The Al-5Zn-10Sn alloy promotes faster hydrogen generation, and finer microstructures within this alloy can increase the hydrogen generation rate by approximately 87 %.