text: Sulfuric acid can be used to produce hydrogen from water:
  The compounds of sulfur and iodine are recovered and reused, hence the process is called the  sulfur–iodine cycle. This process is endothermic and must occur at high temperatures, so energy in the form of heat has to be supplied. The sulfur–iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. It is an alternative to electrolysis, and does not require hydrocarbons like current methods of steam reforming. But note that all of the available energy in the hydrogen so produced is supplied by the heat used to make it.