Take a rock, add water, and voila! You get hydrogen.
This is not the most intuitive of chemical reactions, but scientists at the University of Lyon have found a way to extract hydrogen from water using olivine (a.k.a. peridot), a mineral rock. Making use of a speeded-up version of a geological reaction, the mineral strips water of one hydrogen and one oxygen atom to form serpentine (just like iron takes oxygen out of the air to form iron oxide, i.e. rust). The leftover hydrogen atom is released and could then, theoretically, be captured and used as a clean energy source.
Of course, this reaction does take a little more than simply dunking a rock in water. The researchers heated the minerals in water to a couple of hundred degrees Celsius and added a bit of aluminium oxide (ruby) to the mix to provide aluminium atoms. Finally the whole mix was placed into a ‘pressure cooker’: placed between two transparent diamonds and compressed to 2,000 times the pressure of the atmosphere on Earth.
This process occurs in the rocks on the ocean floors around the globe, but this method is a fast-track way to grab hydrogen from naturally-occurring sources.