In the past, I gave some tips on teaching about fuel cells. The main advantage of fuels cells over rechargeable batteries is energy density: Rechargeable batteries must carry with them all components of the oxidation-reduction reaction that generates current. In contrast, fuel cells vehicles are lighter because (like combustion engines) they only need to transport the reducing agent (what is referred to in plain English as “fuel”). Unfortunately, most fuel cells only run on hydrogen. This article containing this chart sums up why they hydrogen economy is much less sustainable when it is compared with current electric vehicle technology. Nonetheless, the fact that fuel cells are so remarkably efficient at converting chemical energy merits research into cells that run on fossil fuels. This article is well over a year old, but it is noteworthy that this company is pursuing research into fuel cells that run on natural gas. The Redox Company currently proposes using these fuel cells for generating electricity in residences and businesses. However, given the cost-effectiveness of natural gas cars, the next logical step is to apply this technology to transportation.