Hall–Héroult process
Hydrogen can be produced using aluminium by reacting it with water. To react with water, however, aluminium must be stripped of its natural oxide layer, a process which requires pulverization, chemical reactions with caustic substances, or alloys. The byproduct of the reaction to create hydrogen is aluminum oxide, which can be recycled back into aluminium with the Hall–Héroult process, making the reaction theoretically renewable. However, this requires electrolysis, which consumes a large amount of energy