The team from the University Claude Bernard in Lyon, France, used aluminium oxide to speed up the process by which hydrogen is naturally produced when water interacts with olivine, a common type of rock, under high temperatures and pressures found deep underground.

Published recently in the journal American Mineralogist, the discovery could pave the way for considerably cheaper hydrogen production. Used in rockets and in battery-like fuel cells, hydrogen is being widely researched as a non-polluting fuel. Fuel cells, which meld hydrogen with oxygen in the air to yield electricity, emit only water, which makes them attractive as a way to cut greenhouse gas emissions and air pollution. The high costs of its production, however, have been hindering its wider deployment.