The commercially available carbon gas diffusion electrodes (GDEs) with low specific active area but high permeability are often used as Br-2 electrodes in the H-2-Br-2 fuel cell. In order to increase the specific active surface area of the existing carbon GDEs, a study was conducted to grow multi-wall carbon nanotubes (MWCNTs) directly on the surface of carbon fibers of a commercial carbon electrode. Experimental fixtures were developed to promote the electrodeposition of cobalt and the growth of MWCNTs on the carbon GDE. The MWCNT growth across the carbon electrode was confirmed by SEM. The carbon GDE with a dense distribution of short MWCNTs evaluated in a H-2-Br-2 fuel cell has 29 times higher active surface area than a plain carbon electrode and was found to be highly durable at an electrolyte flow rate of 10 cc/min/cm(2). The performance of the best single layer MWCNT GDE measured at 80% discharge voltage efficiency in a H-2-Br-2 fuel cell was found to be 16% higher compared to that obtained using three layers of plain carbon electrodes. Finally, the preliminary material cost analysis has shown that the MWCNT-based carbon electrodes offer significant cost advantages over the plain carbon electrodes. (C) The Author(s) 2015. Published by ECS. All rights reserved.