Nanotube Thermocell Harvests Waste Heat

Energy lost as low-grade heat in industrial waste streams or derived from geothermal activity might be practically and cost-effectively harvested as electrical energy thanks to a new type of thermo-electrochemical cell. The device, known colloquially as a thermocell, makes use of multiwalled carbon nanotubes (MWNTs) as relatively inexpensive carbon electrodes (Nano Lett., DOI: 10.1021/nl903267n). A team led by Ray H. Baughman of the University of Texas, Dallas, developed the thermocells, which use the ferri/ferrocyanide redox couple. The MWNT electrodes “provide high electrochemically accessible surface areas and fast redox-mediated electron transfer, which significantly enhances thermocell current generation capacity and overall efficiency,” according to the researchers. By growing the nanotube electrodes in vertically aligned “forests,” efficiency can be further boosted so that the devices are three times more efficient than conventional thermocells with platinum electrodes. Baughman’s thermocells were made in several practical configurations, including cells that can be wrapped around exhaust pipes. “The enhanced thermocell performance demonstrated in this study using MWNT electrodes suggests that other nanostructured electrode materials might also be applied to significantly enhance the efficiency of thermocell devices,” the researchers note.