We report the tuning of the catalytic activities of Pt nanoparticles decorated multi-walled carbon nanotubes (Pt/MWCNTs) toward ethanol oxidation reaction by assembling with functionalized carbon nanotubes (f-MWCNTs) matrices. The optimization process was carried out with two distinct assembly structures: grafted and multilayered. By varying the assembly directions of f-MWCNTs with different types of functional groups, the interactions between the matrix and Pt/MWCNTs were significantly changed, and therefore the ethanol oxidation reaction kinetics. Interestingly, the grafted structure had double the catalytic activity and stability than the multilayered structure loaded with the same amount of Pt/MWCNTs and f-MWCNTs. Further investigation on reaction kinetic and effect of the ratio between f-MWCNTs and Pt/MWCNTs suggested that the catalytic performance of each structure depends strongly on the non-covalent interactions among functional groups on the matrix surface, reactants, intermediates and the Pt active surface. These dependencies, in turn, are stronger for the grafted than the multilayered structure. Basing on the effects of changing reaction parameters, we propose that the grafted structure acts like a natural enzymatic catalyst while the multilayer structure performance resembles the conventional alloy catalysts. (C) 2013 The Electrochemical Society. All rights reserved.