Protoype fuel cell on left of battery. Each black dot in the center of the white circles are the "fuel-cell" (via Harvard University)
Unlike Energizer batteries, which may last and last (according to the commercials anyway), a team of scientists from Harvard University have designed a fuel-cell on the same premise. However unlike the bunny-represented company, their fuel-cell can keep running even after its power source has drained. The scientists designed the solid-oxide fuel cell (SFOC) to convert hydrogen into electricity which can also be stored for later use, such as when it runs out of fuel.
The secret to their success lies in the cell’s anode (negative) electrode. Typically the anode/cathode connections in thin-film fuel-cells are made from platinum which is able to generate power after the fuel runs out through an additional chemical reaction about 15 seconds long. However, if those same platinum-based electrodes are layered with another compound, the stored energy becomes much larger. In order to increase the amount of power the SFOC can store, the scientists designed the cells electrodes using a multilayered system that uses porous platinum as the cells cathode with an electrolyte, called yttria-stabilized zirconia (which is a zirconium-oxide based ceramic), that is used to separate the two electrodes. Finally, the anode layer is comprised of vanadium-oxide which acts as a catalyst for aerobic oxidation reactions. Using the bilayered compound along with the platinum allowed the cell to generate additional power for 3 minutes and 30 seconds (with a current density of 0.2 mA/cm2) compared to just using platinum alone.
Composition of the fuel-cell (via Harvard University)
According to associate professor Shriram Ramanathan, lead scientist, there are three possibilities as to why the cell is able to generate additional power (they’re not actually sure why as of yet).
The reasons speculated on all entails the use of vanadium-oxide as the cells anode connection. The first reason is actually fact and entails the oxidation vanadium ions as the chemical reaction of hydrogen occurs. The team verified this reaction through x-ray photoelectron microscopy. The vanadium oxidation combined with the porous platinum is not capable of generating the 3 minute+ of additional electrical current. The second possibility involves the vanadium-oxide’s nano-crystaline structure where ‘run-off’ hydrogen may get trapped, stored and eventually oxidized at the anode connection. The third reason the team speculated on involves the different concentrations of oxygen ions collected at both the cathode and anode which create oxygen anions that oxidize resulting in additional current being generated. Whatever the actual reason(s) might be, the team states that a more advanced fuel-cell design will be available for testing with micro-UAV’s within the next 2 years where the new technology could be beneficial.