An Inspirational Brew
Prakash discovers beer-making process can improve fuel cells
By Eva Emerson
USC College chemist G.K. Surya Prakash is not a drinker. But he has been known to indulge in a nonalcoholic (NA) beer once in a while.
Like many, Prakash, holder of the George A. and Judith A. Olah Nobel Laureate Chair in Hydrocarbon Chemistry, wondered how brewers remove the alcohol from NA beer. Curious, he probed the scientific literature and learned that the industry uses a semipermeable membrane to selectively filter alcohol (ethanol) from beer.
He was struck by an idea: Perhaps he could use a similar technique to create a better membrane for the liquid-methanol fuel cell. After all, a major obstacle that he and his colleagues—including Nobel Laureate George Olah—had come up against in developing the fuel cell involved a leaky membrane. What if he could engineer a membrane that selectively blocked methanol, ethanol’s chemical cousin?
Honed by the team, the idea worked. Last fall, USC received a patent for the new membrane, which has led to critical improvements in the team’s fuel cell.
“Our membrane is cheaper and less leaky and offers a quantum leap in terms of efficiency,” Prakash says. “It represents a major breakthrough in terms of commercializing the methanol fuel-cell technology.”
Since 1989, Prakash and Olah, holder of the Donald P. and Katherine B. Loker Chair in Organic Chemistry and director of the USC Loker Hydrocarbon Research Institute, have worked with NASA’s Jet Propulsion Laboratory (JPL)/Caltech to develop the methanol fuel cell as part of a project funded by the Defense Advanced Research Projects Agency.
To demonstrate the promise of the fuel cell, Prakash holds up a plastic bottle half-filled with liquid. A plastic pen squeezed in its top holds a red toy propeller. He inverts the bottle, and within seconds the propeller starts spinning. There’s no noise, no smoke, no heat. Set right side up, the propeller continues to whirl for 80 minutes, powered by the USC/JPL-patented fuel cell with the new membrane embedded in the cap.
The membrane lies at the heart of the methanol fuel cell—essentially a battery that converts chemical energy to electrical energy. It is coated with small amounts of platinum on graphite on one side (cathode) and platinum-ruthenium on graphite on the other (anode). The anode holds a reservoir of liquid methanol and water; the cathode is exposed to air (oxygen). The metal catalysts at the anode trigger a reaction between methanol and water to produce hydrogen (protons), electrons and carbon dioxide. As electrons travel through a wire connecting the anode and cathode, they produce electricity. To complete the circuit and produce energy, protons pass through the membrane to the cathode side, where they react with oxygen and electrons to form water.
The old membrane, the commercially made Nafion, allowed protons to pass through easily but also let liquid methanol and excessive water move across the barrier and degrade the fuel cell’s overall performance. In addition, Nafion costs $900 per square meter.
The new membrane is made of a material that, when wet, feels like seaweed. The team created it by mixing a polymer (PSSA) with a polymer matrix (PVDF) similar to nonstick coating used on pans. The team makes the new membrane in the lab and estimates that it costs under $10 per square meter.
Incorporating the new membrane has increased the fuel cell’s energy efficiency by 10 percent, bringing the total efficiency to 35 percent at room temperature. An average internal combustion engine’s efficiency is 18 percent.
A number of companies already have announced plans to use liquid-methanol fuel cells, which are much easier to handle than fuel cells powered by hydrogen gas and can be recharged simply by adding a cartridge of liquid methanol. Toshiba currently is working on building laptop computers powered by the technology. |
