A team of scientists has developed a highly efficient catalyst for extracting electrical energy from ethanol, an easy-to-store liquid fuel that can be generated from renewable resources. These scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory and the University of Arkansas have described the catalyst in the Journal of the American Chemical Society steers the electro-oxidation of ethanol down an ideal chemical that releases the liquid fuel's full potential of stored energy.
The Brookhaven Lab chemist who led the work, Jia Wang, said that this catalyst is a game changer that will enable the use of ethanol fuel cells as a promising high-energy-density source of 'off-the-grid' electrical power.
Wang noted that ethanol fuel cells are lightweight compared to batteries. They would provide sufficient power for operating drones using a liquid fuel that is easy to refill between flights, even in remote locations.
The carbon-carbon bonds are where much of ethanol's potential power is locked up that form the backbone of the molecule. The catalyst Wang's team developed shows that breaking those bonds at the right time is the key to unlocking that stored energy.
Wang noted that the electro-oxidation of ethanol could produce 12 electrons per molecule. However, the reaction can progress by following many different pathways.
The results of most of these pathways are incomplete oxidation: the catalysts level carbon-carbon bonds intact, releasing fewer electrons. Also, they strip off hydrogen atoms early in the process, exposing carbon atoms to the formation of carbon monoxide, which "poison" the catalysts' ability to function over time.
Noted further, Wang said that the 12-electron full oxidation of ethanol requires breaking the carbon-carbon bond at the beginning of the process, while hydrogen atoms are still attached because the hydrogen protects the carbon and prevents the formation of carbon monoxide. Then, multiple steps of dehydrogenation and oxidation are needed to complete the process.
The new catalyst has the combination of reactive elements in a unique core-shell structure that Brookhaven scientists have been exploring for a range of catalytic reactions to speed up all of these steps.
For the catalyst to be created, Jingyi Chen of the University of Arkansas, who was a visiting scientist at Brookhaven during part of this project, developed a synthesis method to co-deposit platinum and iridium on gold nanoparticles. The platinum and iridium form "monatomic islands" across the surface of the gold nanoparticles. Chen noted that the arrangement is the key that accounts for the catalyst's outstanding performance.
