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A fuel cell (FC) generates electricity by chemical reactions. The catalyst dispersion in Membrane electrode assembly (MEA) is a crucial factor among various factors to affect the performance of a FC. A novel grafting method is adopted in this study to grow secondary carbon nano-tubes (CNTs) on a substrate comprised of primary CNTs, in order to form branchy CNTs with higher specific surface area (SSA). The as-obtained branchy CNTs are then used as catalyst carriers in the MEA of Direct methanol fuel cell (DMFC). The SSA of primary CNTs is 285 m2/g. After grafting, the SSA of the branchy CNTs is raised to 436 rn2/g. An self-assembled DMFC of air-breathing type with active MEA area of 2 x 2 cm2/g is used in this study as the standard FC for the electrical performance test The peak power of DMFC comprised of an MEA with sole primary CNTs is 0.002 watts at 0.15 V. Such peak power can be increased up to 0.01 watts at 0.4 V while replacing the MEA with the new branchy CNTs. The open circuit voltages (OCVs) are 0.4 V and 0.6 V for DMFCs with ME As of sole primary CNTs and branchy CNTs, respectively.