Design of ternary Al–Sn–Fe alloy for fast on-board hydrogen production, and its application to PEM fuel cell

An Al–Sn–Fe alloy is designed to increase the hydrogen generation rate even in weak alkaline water through the effective removal of Al oxide. Al-1wt.%Sn-1wt.%Fe alloy exhibits the hydrogen generation rate about 6 times higher than pure Al and 1.6 times higher than Al-1wt.%Fe alloy. Increases in exchange current density of Al alloys are in good accordance with increases in hydrogen generation rate. The addition of Sn in Al–Fe alloy can increase the hydrolysis rate by accelerating the breakdown of passive film (Al(OH)3 and Al2O3) in an alkaline solution. Hence, the Al-1wt.%Sn-1wt%Fe alloy shows a much higher hydrogen generation rate than pure Al and Al-1wt.%Fe alloy in relatively weak alkaline water. In the hydrolysis of Al-1wt.%Sn-1wt%Fe, Fe accelerates the hydrogen production by inducing simultaneously both inter-granular and galvanic corrosion, whereas Sn increases the hydrogen generation rate by breaking the Al oxide down effectively. Based on the increase in the hydrogen generation rate of Al-1wt.%Fe and Al-1wt.%Sn-1wt%Fe alloys over pure Al, the contribution to the increase of Fe and Sn are calculated to be 63% and 27%, respectively. Because the same amount of power is obtained by PEMFC using 6 times less Al–Sn–Fe alloy than pure Al, the weight and volume of on-board hydrogen production reactor can be reduced significantly by alloying Al with a small amount of Fe and Sn.