Hydrogen cars Can a clean gas fuel really overtake batteries on the road to net zero?

Hydrogen is a beguiling substance: the lightest element, when it reacts with oxygen it produces only water and releases abundant energy.

- Jasper Jolly

The invisible gas looks like a clean fuel of the future. Some of the world's top automotive executives are hoping it will dethrone the battery as the technology of choice for zero-emissions driving.

Our EV Mythbusters series has looked at concerns ranging from car fires to battery mining, range anxiety to cost concerns and carbon footprints. Today, we ask: could hydrogen offer a third way and overtake the battery?

The claim Many of the strongest claims for hydrogen's role in the automotive world come from industry chief executives. The Japanese firm Toyota is the most vocal proponent of hydrogen, and its chair, Akio Toyoda, last month said he believed the share of battery cars would peak at 30%, with hydrogen and internal combustion engines making up the rest. Toyota's Mirai is one of the few hydrogen-powered cars that is widely available, alongside the Nexo SUV from Hyundai in South Korea.

Oliver Zipse, the boss of BMW, said last year: "Hydrogen is the missing piece in the jigsaw when it comes to emission-free mobility." BMW may be investing heavily in battery technology, but the company has its BMW iX5 Hydrogen car in testing - albeit using Toyota fuel cells. Zipse said: "One technology on its own will not be enough to enable climate-neutral mobility worldwide."

The science Zero-emissions "green hydrogen" comes from electrolysis: using clean electricity to split water into hydrogen and oxygen.

To use hydrogen as a fuel it can be burned, or it can be used in a fuel cell: the hydrogen reacts with oxygen from the air in the presence of a catalyst (often made from platinum). That strips away electrons that can run through an electric circuit, charging a battery that can power an electric motor.