In the near term, the most likely fuels for mobile fuel cells (which are primarily of the PEM type) are reformed gasoline, propane, and methanol, all of which contain significant amounts of hydrogen. Sadly for cruising sailors, diesel's complex molecular structure makes it especially difficult to extract the hydrogen, so future research efforts will likely focus on other readily available fuels. But these fuels present their own special problems.
Ordinary gasoline is comparatively high in sulfur, which chokes the PEM's catalyst, so it can't be used in fuel cells. It must first be scrubbed of sulfur and other additives that are beneficial to internal combustion engines but toxic to fuel cells. This renders existing fuel refining, storage, and distribution systems incompatible for use with fuel-cell-powered vehicles.
But hydrocarbon fuels aren't the only option. One solution to the fuel issue involves storing hydrogen in the form of metal hydride in fuel cylinders. Another involves storing hydrogen in the form of sodium borohydride liquid, which is nonflammable and nontoxic. After being catalyzed, hydrogen is produced, along with sodium metaborate, which is essentially borax. Chrysler has fitted one of these borax-powered fuel cells into a minivan, which began testing last April.