Over the past decade, most of the world’s major automakers have expended a lot research dollars and engineering resources on developing vehicles that burn hydrogen. There are two basic approaches to using hydrogen in vehicles: the proton exchange membrane fuel cell and the classic internal combustion engine.
The primary reason for using hydrogen in internal delivery valve combustion engines is that they already exist and are comparatively inexpensive. Since hydrogen combusts fairly readily, it doesn’t take much in the way of modifications, mainly new fuel injectors and a storage system. While the basics are the same, the combustion properties of hydrogen are very different from gasoline or diesel. It burns much faster than those fuels, so getting the most out of hydrogen.
The preferred approach to using hydrogen long term is the fuel cell. Fuel cells use a process that is essentially the reverse of electrolysis to combine hydrogen and oxygen in the presence of a catalyst to generate electricity. The main problem with fuel cells is the cost. Until now, fuel cells have been largely hand made one at a time which greatly increases the cost of manufacturing. Now that the basic technology premise of fuel cells has been proven out, automakers are working to design fuel cell stacks that integrate ancillary systems such as cooling, water drainage and fuel delivery. These units, such as GM’s latest fifth generation stack, are designed to be mass produced on automated nozzle equipment at much lower cost.
The other cost factor for fuel cells is the catalyst. The plates that make up the working part of a fuel cell plunger stack are coated with platinum, which is of course very expensive. Most automakers are reluctant to give details of the internals of their stacks but GM recently revealed that its fourth generation fuel cell stack used in the Chevy Equinox contained 80 grams of platinum. Its next-generation stack contains only 30 grams and the upcoming iteration is expected to need less than 10 grams, putting it on a par with catalytic converters.