Researchers added aluminium to the natural "serpentinisation" process and found they could liberate hydrogen up to 50 times faster than occurs in nature.
Scaling up the experiment could help to meet the world's future energy needs without adding to greenhouse gases and climate change, the scientists claim.
But some major technical hurdles will have to be crossed, notably finding an economic way to achieve the huge pressures involved.
Hydrogen, a constituent of water, not only powers rockets and "clean" road vehicles but can be used to generate electricity. Burning it makes just water vapour.
The element should be a perfect clean energy source, but production methods are too energy-thirsty, costly, and bad for the environment.
The new process could tip the balance and make large-scale hydrogen power a much more practical prospect, it is claimed.