Solid acids, however, are conductive at about 250 °C, which is hot enough that the catalyst can withstand impurities in the fuel. Superprotonic's prototype 50-watt fuel-cell stack can run on any fuel that can be reformed into hydrogen, says Calum Chisholm, the company's vice president and founder. Because a catalyst's activity increases with increased temperature, future solid-acid fuel cells may operate with much less catalyst, or with less-expensive catalysts that are not active below 100 °C. "Other materials become active at this temperature, including nickel, cobalt, and iron," says Chisholm.

However, the technology is young and has a way to go before it reaches its potential. "There's been a lot of work on the structure of electrodes to improve the performance of other types of fuel cells," says Robert Savinell, a chemical engineer at Case Western Reserve University, who is not affiliated with Superprotonic. Haile says that the solid-acid technology is nowhere near as efficient as it can be, and that it's merely a matter of time before it catches up with polymer-based systems. Superprotonic is still making its cells one at a time and by hand, using more platinum catalyst than other kinds of fuel cells require. Haile says that, in the meantime, she and her Caltech colleagues are "trying to see if we can come up with better catalysts with higher surface areas. That's a milestone the company needs to reach."

Eventually, Superprotonic hopes to develop fuel-cell-based residential and commercial "cogeneration" systems, which would use natural gas or other common fuels to generate electricity and waste heat to heat water. However, given the current economy and the disappointment that has surrounded fuel cells over the past 20 years or so, the company is proceeding cautiously. "What we can give somebody right now," says Chisholm, is a 50-to-250-watt battery recharger or electrical generator for camping or military use that employs what he calls "real-world fuels." Superprotonic has funding from the military to develop a battery charger and is talking with other companies about commercializing a civilian version of it.