Charge Density Modulated Shape-Dependent Electrocatalytic
Activity of Gold Nanoparticles for the Oxidation of Ascorbic Acid
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Abstract
The electrocatalytic performance
of noble metal nanoparticles depends
upon their size, shape, composition, and crystalline facets. Here
we demonstrate the shape-dependent electrocatalytic activity of Au
nanoparticles toward ascorbic acid oxidation in acidic medium, wherein
the catalysis is strongly influenced by the shape of the nanoparticles.
The synthesis of (popcorn, tetrapod, and bipod shaped) Au nanoparticles
was carried out using a systematic variation of the surfactant concentrations
based on the seed-mediated growth technique at room temperature. Due
to the facile electrostatic interaction of the positively charged
Au nanoparticles with glassy carbon electrode, the modification of
the surface with variable-shaped Au nanoparticles is accomplished
without involving any binding agents. Among variable-shaped face-centered
cubic (fcc) crystalline AuNPs, bipod-shaped Au nanoparticles (GNBipd)
exhibit a superior electrocatalytic performance over tetrapod-shaped
(GNTepd) and popcorn-shaped (GNPop) nanoparticles as inferred from
the differential pulse voltammetry and electrochemical impedance spectroscopy.
The results have been explained by invoking the relative surface free
energy (γ) with preferentially exposed crystal planes, relative
surface area (<i>A</i>), zeta potential (ξ), and the
curvature-induced charge density (σ<sub>q</sub>) at the apex
for individual variable-shaped gold nanoparticles