A quick recipe for producing hydrogen by speeding up a chemical reaction that occurs in rocks holds out the promise of abundant clean energy in the future, experts believe.
Researchers added aluminium to the natural “serpentinisation” process and found they could liberate hydrogen up to 50 times faster.
Scaling up the experiment could help to meet the world’s future energy needs without contributing to greenhouse gas emissions and climate change, the scientists claim.
However, some major technical hurdles will have to be crossed first – notably an economic way to achieve the enormous pressures involved.
Hydrogen, a constituent of water, not only powers rockets and “clean” road vehicles but can be used in fuel cells to generate electricity. When hydrogen is burned, all that is emitted is water vapour.
In theory the element should be a perfect source of clean energy, but current 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.
“Aluminium’s ability to catalyse hydrogen production at a much lower temperature could make an enormous difference, ” said Dr Jesse Ausubel, a member of the team from The Rockefeller University in New York City.
Serpentinisation occurs when water and olivine meet in hot conditions under great pressure. Olivine is a yellow-green coloured mineral made of magnesium, iron, silicon and oxygen.
The process divorces hydrogen molecules from oxygen atoms in water. At the same time, olivine is transformed into another mineral, serpentine, characterised by a scaly green-brown appearance reminiscent of snake skin.
Scientists from the Deep Carbon Observatory, an international collaboration of experts investigating the inner workings of the Earth, reproduced the process in a tiny diamond-enclosed “anvil cell” about as wide as a pencil lead.
The inside of the cell was heated to 200C-300C and subjected to pressure of two kilobars, equivalent to twice that found at the bottom of the deepest ocean.
Adding aluminium oxide accelerated the reaction, so instead of taking months it happened overnight.
The findings were presented at the annual autumn meeting of the American Geophysical Union in San Francisco, US.
Dr Ausubel pointed out that methods of hydrogen production usually involve the conversion of methane, which produces the greenhouse gas carbon dioxide as a byproduct.
Alternatively, water molecules can be split at 850C or more, requiring a lot of energy and careful engineering.
The cost and risk would “drop a lot” if the serpentinisation technique could be developed, said Dr Ausubel.
He added: “Scaling this up to meet global energy needs in a carbon-free way would probably require 50 years. But a growing market for hydrogen in fuel cells could help pull the process into the market.”
Fuel cells produce electricity by converting hydrogen and oxygen into water.