Hydrogen fuel cell technology Hydrogen fuel-cell technology is another area pioneered by ExxonMobil and its research partners. Hydrogen molecules, or H2, are highly efficient energy carriers which, when used in a fuel cell, emit only water vapor from the tailpipe. Hydrogen-powered fuel cell vehicles could improve energy use and lower carbon emissions, bringing important benefits for consumers, the environment and energy security. But on Earth hydrogen molecules rarely exist by themselves. They must be made from other compounds and then delivered efficiently to be used for vehicle fuel cells. ExxonMobil is developing an innovative on-board hydrogen-powered fuel cell system that converts conventional hydrocarbon fuels such as gasoline or diesel into hydrogen for a fuel cell right under a vehicle’s hood. This new technology, which will be applied first to industrial vehicles such as forklifts, converts traditional hydrocarbon fuels, such as gasoline or diesel, into hydrogen directly on board a vehicle, eliminating the need for separate facilities for producing and distributing hydrogen. Measured on a “well-to-wheels” basis, this on-vehicle hydrogen fuel system could be up to 80 percent more fuel-efficient, and emit 45 percent less carbon dioxide, than today’s internal-combustion engine. Ongoing advances in vehicle and fuel technology will be critical to meeting global demand for transportation fuels. They will also help address the risk posed by rising greenhouse-gas emissions.