Rapid Microwave-Assisted Polyol
Reduction for the
Preparation of Highly Active PtNi/CNT Electrocatalysts for Methanol
Oxidation
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Abstract
PtNi nanoparticle
catalysts supported on oxygen functionalized
carbon nanotubes were prepared by microwave-assisted polyol reduction
using two different modes of irradiation, namely, continuous or pulsed
irradiation. The influence of irradiation time or pulse number on
catalyst structure and activity in methanol electrooxidation has been
studied. Characterization was done with ICP-OES, XRD, TEM, XPS, and
XAS to determine composition, morphology, crystal structural and chemical
state. The electrocatalytic activity has been evaluated by cyclic
voltammetry (CV) and chronoamperometry (CA). PtNi nanoparticles are
present in alloy form and are well dispersed on the carbon nanotubes.
Pt is in its metallic state, whereas Ni is present in metallic and
oxidized form depending on the preparation conditions. The electrocatalytic
activity both in terms of surface and mass specific activity is higher
than that of the state-of-the-art-catalyst Pt/C (E-TEK). The enhancement
of the electrocatalytic activity is discussed with respect to PtNi
alloy formation and the resulting modification of the electronic properties
of Pt by Ni in the alloy structure. The microwave assisted polyol
method with continuous irradiation is more effective in the preparation
of PtNi electrocatalysts both in terms of reaction time and activity
than the pulsed microwave method