Hydrocarbon fuels obstacles

Although it is attractive to directly convert chemical energy to electricity, PEM fuel cells face significant practical obstacles. Expensive heavy metals like platinum are typically used as catalysts to reduce energy barriers associated with the half-cell reactions. PEM fuel cells also cannot use practical hydrocarbon fuels like diesel without complicated preprocessing steps. Those significantly increase the complexity of the overall system. At this time, it appears likely that PEM fuel cells will be confined to niche applications where high cost and special fuel requirements are tolerable. 

Hydrogen gas is the preferred fuel for low-temperature fuel cells. The main obstacle in the use of hydrogen as energy carrier is that hydrogen is not a readily available fuel. In high-temperature fuel cells, a hydrocarbon fuel, for example, methane or gasoline, can be fed directly into the cell. To use hydrocarbons... 

Oxygen difluoride (OF2) is an attractive oxidizer for many fuels (II, 16), especially hydrocarbons, because it provides the optimum O/F ratio for hydrocarbon oxidation. Since it is denser than the equimolar 02-F2 mixture (Flox), it should be easier to handle and should perform better. However, OF2 has been expensive to make because the usual preparation from F2 plus base (18) converts half the F2 to F . Consequently, the less attractive but lower cost Flox mixtures have received more attention. A better synthesis for OF2 would remove this obstacle and justify a more thorough investigation of its performance. 

The prognosis, then, for road transportation is for a varied mix of propulsion systems and fuels as conventional petroleum becomes less plentiful and prices rise. Internal combustion engines operating with synthetic liquid fuels (hydrocarbons, alcohols and bio-diesel) are expected to appear in increasing numbers, often supported by hybrid electric drives to reduce fuel consumption. Plug-in hybrid electric vehicles may become popular when more durable and affordable batteries become available. This would allow the power source to be part liquid fuel and part mains electricity. Some of the major obstacles to be overcome with hydrogen-fuelled vehicles are ... 

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