Palladium nanoparticles and nanowires deposited electrochemically: AFM and electrochemical characterization |
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Authors: | Victor C Diculescu Ana-Maria Chiorcea-Paquim Oana Corduneanu Ana Maria Oliveira-Brett |
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Institution: | (1) Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-535 Coimbra, Portugal |
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Abstract: | Palladium nanoparticles and nanowires electrochemically deposited onto a carbon surface were studied using cyclic voltammetry,
impedance spectroscopy and atomic force microscopy. The ex situ and in situ atomic force microscopy (AFM) topographic images
showed that nanoparticles and nanowires of palladium were preferentially electrodeposited to surface defects on the highly
oriented pyrolytic graphite surface and enabled the determination of the Pd nanostructure dimensions on the order of 50–150 nm.
The palladium nanoparticles and nanowires electrochemically deposited onto a glassy carbon surface behave differently with
respect to the pH of the electrolyte buffer solution. In acid or mild acid solutions under applied negative potential, hydrogen
can be adsorbed/absorbed onto/into the palladium lattice. By controlling the applied negative potential, different quantities
of hydrogen can be incorporated, and this process was followed, analysing the oxidation peak of hydrogen. It is also shown
that the growth of the Pd oxide layer begins at negative potentials with the formation of a pre-monolayer oxide film, at a
potential well before the hydrogen evolution region. At positive potentials, Pd(0) nanoparticles undergo oxidation, and the
formation of a mixed oxide layer was observed, which can act as nucleation points for Pd metal growth, increasing the metal
electrode surface coverage. Depending on thickness and composition, this oxide layer can be reversibly reduced. AFM images
confirmed that the PdO and PdO2 oxides formed on the surface may act as nucleation points for Pd metal growth, increasing the metal electrode surface coverage.
Dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday. |
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Keywords: | Palladium nanoparticles and nanowires AFM Voltammetry Impedance spectroscopy Hydrogen Oxide Pre-monolayer |
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