Single wall nanohorns as electrocatalyst support for vapour phase high temperature DMFC

The use of single wall nanohorns (SWNH) as electrocatalyst support has proved to increase the performance of polymer electrolyte membrane-based fuel cells. In order to investigate in more detail such behavior, the electrochemical characterization of SWNH based electrodes was performed. The use of SWNH in vapour phase high temperature direct methanol fuel cells (HT-DMFC) was also addressed. Cyclic voltammetry experiments have indicated a higher electrochemical activity towards methanol electro-oxidation and a higher tolerance to carbonaceous species accumulation for a SWNH based electrode than for carbon black and commercial corresponding ones. Carbon black electrode presented a better performance than SWNH one for oxygen reduction reaction at low current densities while, at higher overvoltages, SWNH electrode performed better. The exact role of the improved performance of SWNH based electrodes is yet not clear but may be related to a higher water vapour adsorption or electrode morphology. Vapour phase HT-DMFC operation showed the improved performance of the SWNH electrode in agreement with previous works and with the electrochemical characterization performed during this work; despite the higher ohmic resistance observed in comparison with the carbon black based electrode. Moreover, SWNH based electrode showed improved fuel cell stability during longer operation times.