The effect of amine functionalized carbon nanotubes as promising support for platinum nanoparticles on oxygen reduction reaction

In this study, multi-wall carbon nanotubes (MWCNTs) are chemically oxidized (OMWCNTs) and functionalized with ethylenediamine (EDAMWCNTs) and diethylenetriamine (DETAMWCNTs) as amine precursors. The electrocatalysts were prepared through deposition of Pt nanoparticles on the functionalized MWCNTs by polyol method. The average size of Pt nanoparticles was found to be between 4 and 5 nm. Cyclic Voltammetry (CV), Rotating Disk Electrode (RDE), Electrochemical Impedance Spectroscopy (EIS), and Chronoamperometry (CA) were employed to evaluate the electrochemical properties of the electrocatalysts. The Electrochemical Active Surface Area (EASA), number of electrons transferred (n), and onset potential of EDAMWCNTs and DETAMWCNTs were found to be about 32.2 and 45.8 (m^2/g Pt), 4.03 and 4.10 (electron per oxygen molecule), and 0.986 and 0.997 (V vs. RHE), respectively. However, in the case of Pt-OMWCNTs, the above-mentioned electrochemical characteristics were calculated to be 24.2 (m^2/g Pt), 3.34 (electron per oxygen molecule), and 0.824 (V vs. RHE), respectively. Moreover, EIS and CA indicate that introducing amine functional groups leads to low electron transfer resistance and better electrocatalytic activity and stability during oxygen reduction. The results show that the more the number of nitrogen atoms within the amine functional groups is, the more enhanced the electrocatalytic performance of Pt nanoparticles in ORR will be.