In the furious race to perfect fuel cells for use in electric cars and other commercial products, researchers from the California Institute of Technology may have now taken the lead, describing in today's issue of Nature an intriguing new design. Sossina Haile and colleagues created the novel fuel cell by combining features from existing "hot" and "cold" cells. As their names imply, these devices operate only at temperatures above 600 degrees Celsius or below 100 degrees Celsius, respectively. The new hybrid, though, runs at temperatures right in between, potentially making it more suitable for a range of applications.

All fuel cells follow the same general plan: two electrodes (an anode and a cathode) sandwich an electrolyte, made from a polymer or some other material that allows ions, but not electrons, to pass through it. A hydrogen-containing fuel flows to the anode and loses its electrons. These electrons travel through an external circuit while the resulting positive ions pass through the electrolyte. At the cathode, the electrons then combine with the hydrogen ions and oxygen, generating electricity and water as a by-product. The new, warm fuel cell marries a solid electrolyte, such as those found in solid-oxide cells, with the hydrogen-ion conduction used in polymer-electrolyte membrane (PEM) fuel cells. Its developers hope that with some further optimization, the warm fuel cell will create higher voltages at greater efficiencies than its predecessors