various 3-D structured Pt/xrGO-yPolyethyleneimine-functionalized MWCNTs (PMWCNT) were successfully prepared by the hybridization of rGO and PMWCNT. The FE-SEM and TEM images. confirm the 3-D structure of hybridized Pt/rGO-PMWCNT catalyst and dispersion of Pt nanoparticles. In case of Pt/PMWCNT, Pt nanoparticles are preferentially deposited onto the external surface of PMWCNT but upon hybridization, the preferential deposit of Pt nanoparticles onto PMWCNT is not expected due to high affinity of rGO to ward Pt nanoparticles. The Pt content deposited onto the hybridized supporting materials tends to be increased with rGO content. It is noteworthy that the BET surface area is increased with PMWCNT content due to the formation of the 3-D structure. The electrochemical active surface area (ECSA) and durability based on ECSA is also affected by the mass ratio of rGO and PMWCNT, exhibiting the highest ECSA of 32.5 m(2)/g and the least reduction of ECSA after 1200 cycle by Pt/1rGO-1PMWCNT. The cell performance is enhanced by the hybridization with the best cell performance by Pt/1rGO-1PMWCNT. It is therefore, desirable to choose the appropriate mass ratio of rGO and PMWCNT to maximize the electrochemical properties. (C) 2017 Hydrogen Energy. Publications LLC. Published by Elsevier Ltd. All rights reserved.