After fulfilling its duty, the shiny device will need a replacement cartridge of fuel, which will cost a few dollars.

BBC: Four ways to revive a dying mobile phone

Some fuel cells can charge a device roughly 12 times before needing a replacement cartridge of butane (which the US government permits in checked luggage on airplanes).

BBC: Four ways to revive a dying mobile phone

Such materials could be used to make hydrogen cartridges that would slot into fuel-cell cars, making refuelling as simple as pulling into a filling station and swapping an empty cartridge for a full one.

ECONOMIST: Space-age soot