Electrochemical durability of carbon nanotubes at 80°C

Carbon nanotubes (CNTs) have been studied as an alternative catalyst support in polymer electrolyte membrane (PEM) fuel cells. Recent studies showed that CNTs appear to be more resistant to electrochemical corrosion than carbon black (CB). In a previous study, we have demonstrated the room temperature durability of multiwalled CNTs in both non-catalyzed and catalyzed electrochemical oxidations. This paper is to report results conducted at 80 degrees C-an operational temperature of PEM fuel cells. It was found that multiwalled CNTs are still more resistant than CB at the elevated temperature. However, the electrochemical oxidation rate is more rapid than that at the room temperature. As a result, a decrease in oxidation currents was observed with cyclic voltammetry, attributed to that the initial surface oxides were quickly converted to more stable oxides or carbon dioxide due to the high temperature. For CNTs, extended oxidation could not occur, in contrast to CB, because it requires attacking on the intact graphite planes which are corrosion resistant under the experimental conditions. It was found that the kinetics followed different power laws in time for different carbons. (C) 2007 Elsevier B.V. All rights reserved.