Modification of cathode structure by introduction of CNT for air-breathing DMFC

Optimization of the structure and texture of the cathode catalyst layer for air-breathing DMFC has been studied. Application of carbon nanotubes (CNT) as an additive to the cathode catalyst layer resulted in the increase of BET surface area and porosity of the catalyst layer due to filamentous morphology of CNT. Best performance was observed at the intermediate CNT/catalyst ratio of 0.05. I-U polarization and impedance analysis indicated that the faster oxygen reduction reaction at the open cathode is responsible for the power density improvement. Excessive cathode porosity was not favorable due to the decrease of the effective ionic conductivity of the catalyst layer. (C) 2007 Elsevier Ltd. All rights reserved.