Hydrogen generation by splitting water with Al–Ca alloy

A new hydrogen generation material, Al–Ca alloy, is prepared by ball milling method. Results show the prepared Al–Ca alloy can react with to produce hydrogen, but its hydrogen yield is lower. NaCl addition can further greatly improve hydrogen generation of Al–Ca alloys. The amount of NaCl addition and ball milling time depends on the Ca contents of alloys. As the Ca contents of alloy increase, the amount of NaCl addition or ball milling time may be reduced accordingly. Increasing Ca contents, NaCl addition or ball milling time is beneficial to improve the hydrogen generation rate. Al–Ca alloys can react with water to produce hydrogen at the temperature ranging from 10 °C to 80 °C, and simultaneously a great amount of heat is released. With the increase of air exposure time, the dense Al2O3 and CaO layer formed on the surface of alloy particles will reduce the oxidation reaction rate. Chloride ions and sulfate ions can greatly decrease the induction period of hydrogen generation reaction and obviously improve hydrogen generation rate. Ca2+ ions and Mg2+ ions can affect the production of hydrogen due to their strong affinity to OH−, especially Mg2+ ions which greatly decrease the hydrogen yield to 20%.

► The inert oxide film of Al surface is disrupted by adding Ca into Al to form Al–Ca alloy.
► The prepared Al–Ca alloy can rapidly react with water to produce hydrogen.
► NaCl is added as the activator by ball milling to further improve the hydrogen yield of Al–Ca alloy.
► The prepared Al–Ca alloy can react with water at different temperature.