Functionalized multi-walled carbon nanotubes as supporting matrix for enhanced ethanol oxidation on Pt-based catalysts

In this report, we investigated and characterized the effect of organic-based supporting matrix, using functionalized multi-walled carbon nanotubes (f-MWCNTs), toward enhancement of ethanol oxidation reaction (EOR) on Pt-based catalysts. We exploited amine and carboxylic groups since they could induce water adsorption via hydrogen bonding, creating -OHads for further oxidation of toxic intermediates. The results showed that the COOH-MWCNTs supported Pt/MWCNTs enhanced the kinetics of EOR approximately three times more than NH2-R-MWCNTs and the bare Pt/MWCNTs, in terms of oxidation current density and stability. Further, electrochemical impedance spectroscopy (EIS) spectra at different bias potentials showed that f-MWCNTs decreases the adsorption of intermediates species on Pt active surface by creating an “OH-carpet”, and also enhances the charge-transfer kinetic during the EOR. The carboxylic f-MWCNTs supporting matrix performed best. Following this initial study, further improvement in EOR kinetics such as optimizing the functionalization of NTs could be achieved, towards a viable utilization of a direct ethanol fuel cell.

Research highlights
► Effect of f-MWCNTs (f is COOH or NH2) as supporting matrix toward ethanol oxidation on Pt/MWCNTs is first time studied.
► Functional groups create -OHads, thus enhance ethanol dissociative adsorption and oxidization of intermediates.
► Pt/MWCNTs/COOH-MWCNTs is superior to Pt/MWCNTs/NH2-R-MWCNTs and Pt/MWCNTs in enhancing reaction kinetic and stability.