Abstract:
An electrocatalyst plays an important role in the alcohol oxidation
reaction in fuel cells. Palladium based electrocatalysts are one of the
promising candidates for alcohol oxidation in direct alcohol alkaline fuel
cells. This study reports the preparation of metal nanoparticles (Pd, Ni,
and Sn) supported on sulfonated multi-walled carbon nanotubes
(SF-MWCNTs) using a microwave-assisted solvothermal method. The
physical properties of the prepared electrocatalysts were investigated
using several techniques such as TEM, EDX, XRD, FTIR and Raman
spectroscopy. The electrocatalytic behaviour of the SF-MWCNT-Pd and
its mixtures (i.e., SF-MWCNT-PdSnmix and SF-MWCNT-PdNimix) towards
ethanol and ethylene glycol oxidation in alkaline medium were
investigated. The results show that the mixed Pd-based catalysts gave
better electrocatalytic activity than their alloy nanoparticles or Pd
alone. The SF-MWCNT platform gave better electrocatalytic
performance compared to the unsulfonated and commercial vulcan
carbon. Detailed electrochemical studies (involving cyclic voltammetry,
chronoamperometry, chronopotentiometry, and impedance
spectroscopy) prove that the electrocatalytic oxidation of ethanol at
the SF-MWCNT-PdNimix platform is more stable, occurs at lower
potential, and gives lower Tafel slopes, with faster charge-transfer kinetics compared to its SF-MWCNT-PdSnmix counterpart. The results
also revealed that SF-MWCNT-PdNimix is more tolerant to CO poisoning
than the SF-MWCNT-PdSnmix during ethanol oxidation in alkaline
medium. However, the SF-MWCNT-PdSnmix electrocatalyst showed
better electrocatalytic behaviour for ethylene glycol oxidation in
alkaline medium; with high current response, better stability and low
Tafel slopes. Both (SF-MWCNT-PdNimix and SF-MWCNT-PdSnmix)
electrocatalysts showed comparable behaviour towards CO poisoning
during ethylene glycol oxidation in alkaline medium. The results
obtained provide some important insights into the electrochemical
response of microwave synthesised Pd-based bimetallic catalysts for
potential application in direct alcohol alkaline fuel cell technology.
