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

In this study, multiwall carbon nanotubes (MWCNTs) were 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 lie 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 electron transferred (n), and onset potential for EDAMWCNTs and DETAMWCNTs were found to be about 32.2 and 45.8 (m2/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 (m2/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 lead to less electron transfer resistance and better electrocatalytic activity and stability during oxygen reduction. The results show that the higher number of nitrogen atoms within the amine functional groups the more enhanced electrocatalytic performance of Pt nanoparticles in ORR.